Once the redirect is in place and you have confirmed it is working, you can immediately remove the old site.

I would highly recommend monitoring your sites on a daily basis for 404 errors after the move. Also ensure your 404 page is as helpful as possible. It should contain your normal site's navigation and a search function.

A couple thoughts to add...

A primary reason keywords in your URL are so important is primarily due to their anchor text value. Yes Google will offer a boost but what amplifies this factor is the fact that most links to your site will include the keyword. People can be lazy and lack knowledge, so they link to your site simply by copying and pasting the URL rather then using anchor text. When that happens the URL is the anchor text. So if your domain is shoes.com then every URL link to your site includes "shoes" in it.

Having keywords deeper in your URL is very helpful for several reasons, but they will never match the power of having them in your root URL.

Also, if you are going to restructure your site I strongly recommend you use technology-free URLs. Remove the .html from the end of your URLs.

There are a few reasons for not using technology extensions with urls (i.e. html, htm, php, etc)

• any time you use a redirect there is work involved for you, the server has to check incoming URLs against the list of 301s, etc. They are a normal part of online life, but their use should be minimized. There is a high likelihood you may decide to upgrade your site which would change your .html pages to .php pages. Your URL would be identical except the extension, which would require a 301 for your whole site.

• any time a 301 is used there is a loss of link authority

• the extension is not helpful to users and makes your URLs appear more complex and possibly confusing to users

• a site that shows their extensions is making things easier for anyone who wishes to attack your site. Sure it's a small item, but good security is about taking all the steps you can to make things more difficult for attackers.

With respect to the URL, Google fully understands and adjusts for the slash and dashes in URLs.

how you know it works?

It's fundamental to the concept of anchor text. Take a look at the below two links:

a great site

http://www.seomoz.org/

Both of the above links lead to the same place, the SEOmoz home page. What varies is the anchor text. Google is a multi-billion dollar company. They understand to remove the http:// prefix along with the .org/ suffix.

There are many discussions and resources on this topic. One relevant video from Matt Cutts: http://www.youtube.com/watch?v=gRzMhlFZz9I

I thinking one solution for it. I am going to add manufacturer part number in Title tag rather than URL...

If you take that approach definitely add it to the END of the title, not the beginning. I looked at your site and your page title shows as "53927 Phoenix Copper Waterproof Floor Lamp". Horrible!

The idea of a page title is to allow users to know what the page is about. The item id really shouldn't be part of a title.

The summary of your site is, you are doing far too much too fast. You are not giving your items and pages the attention they require, and your SEO and sales will suffer for it. Your goal is to offer as many products as you can, as fast as possible, as cheaply as possible. This approach directly conflicts with quality measures.

Take one product I found on your site: http://www.vistastores.com/indoorlighting-patiolivingconcepts-53927.html

I understand the product page completely. This is one of 7k+ products you offer. It was likely added to your page as part of a database feed. But look at the URL, the page and it's content. Now take a step back and imagine for a moment you had a small, established lamp shop and this product was one which was added to your store today. Think about adding this page to your site.

The page URL would probably be: http://www.vistastores.com/phoenix-copper-waterproof-floor-lamp. The URL would be much more helpful all around.

Think about the page text. You would describe the lamp itself, maybe offer some examples of it's uses "perfect for intimate lighting in areas near fishtanks, bathrooms, indoor gardens or other areas with higher levels of moisture".

Think about the additional pictures you might provide if this lamp was just one of a few items you sold. You would probably have a few nice displays and can show the lamp in each setting.

The bottom line is, your wish to sell 15k+ products is driving the quality of your site's pages to very low levels. There is almost no unique information on the pages. If you hired someone to spend 2 hours on each and every page making them personal, adding content, etc. the value of those pages to your customers and to search engines would substantially increase. I understand if you can't afford to do it, but you also need to understand your SEO and conversion challenges you will face as a result of "speeding" so fast with an e-commerce site.

Your site has 5k+ errors, 11k+ warnings. My main concern is the 4k+ duplicate pages. The issue is your pages lack content. You need to add unique, relevant, quality content to every page of your site you wish to be indexed.

I would recommend a professional consultation with an SEO. Your site offers very nice products. Your site requires a tremendous amount of SEO attention. Proper SEO can have a dramatic impact on your site's pages being index and your overall sales. If you wish to do-it-yourself, that is possible to but you have a very long way to go. Please check out the Beginner's Guide to SEO.