Change to seo friendly urls problem?

Hi guys im not new in here but i made another user because i didnt like my username.So i read this forum for the past 1 year every day.I learn a lot of thinks.Now i have a problem.I search for an answer but with no success.I have a joomla ecommerce for 2 years now with good backlinks nice serp positions and PR4.But from the bigining i didnt make the urls seo friendly.My question is if i change them now if this will affect my site negative.Im afraid to do that so thats the reason for my question

edit the site has 2000 products

In for answer, I'm in a similar situation with one of my sites.

If you do change them, make sure you update your sitemap.

The truth is that before 5 days i put it in webmaster tools and i didnt submit the sitemap.But my problem and question is if i make this change now will help me or not

It is easy, just use 301 Redirrection. Slowly but sure, your domain will change. But I suggest not. Why would you want to waste your 1 year effort just to change the domain name ?

No i want to change the domain name.I want to change urls to more seo friendly

If you change to another doman you need a 301 redirect (for each page.)

If you're talking about changing the URL 'layout' to something more keyword oriented, then remember you'll also need 301's or you'll lose every bit of link-juice built to those pages.

I don't understand why this is an issue? If you have a PR4, then you obviously don't have an issue with the site. Are you sure this isn't just a personal need to make the site URL's 'prettier' !?

Basic business/marketing 101: If it ain't broke - don't fix it!

Yes sorry i dont want to change the domain only the urls.Yes i think the only reason is as you said to more prettier urls but i dont want to make any troubles to my site.So i think i didnt make any changes Thank you so much for your answer if anyone else have something else to say for my problem here i am