Rewrite URL for big website

[firstjames]

My website is currently have over 1000 000 links indexed by Google , i'm going to rewrite all of these links, is this crazy ? Can someone give me a checklist to avoid going wrong way ? My website: http://www.webtretho.com/forum/

My current url format: webtretho.com/forum/f[forum_id]/[thread-title-thread_id/

Ex:

Old URL:

http://www.webtretho.com/forum/f90/chia-se-dau-hieu-mang-thai-1357342-new/

New URL:

http://www.webtretho.com/forum/chuan-bi-mang-thai/chia-se-dau-hieu-mang-thai-1357342-new/

[firstjames]

Thanks Robert !!!

[RobertFisher]

James, 
I noticed no one had even attempted to answer you and it has been 7 hours. I think there are a couple of reasons for this: the technical level required for url rewriting, the vietnamese language makes understanding a little more difficult (and good move on the url format in english), and there is no reason given as to "why" for the rewrite. So, what do you want to accomplish in making this change?

No one wants to give direction that could potentially lead a site like this down the wrong road. From looking at it, you are getting traffic to it and it seems to do well for you. One note, you might want to get some of your bilingual members to assist google in translating vietnamese as I am sure from using Google Translator, they need the help;)

Here is a link to a post in youMoz that appears to have some excellent info on rewrites. Note that you should also read the comments below as they seem to add a lot to what was posted.

I am fully open to any of the more technically skilled to smack this down, but I wanted you to at least have some direction. Note: If this is your first time at this level of technical change, you might want to consider at least hiring someone to assist you who has been down the road before.

All the best, I hope this provides you with at least a bit of assistance,

Robert

PS - If you do not get what you need here, as a pro member you can use a private question straight to moz. As you will notice from many of the associates to moz that answer here, their level of expertise is very good and they have assisted me on several occasions with good direction to a source or other info.