I don't know how you feel about the DYI thing when it comes to gears, some people don't like the idea of working on transmissions. If the DYI transmission fix idea isn't something that you would rather leave to someone else, here are some resources:
See
http://www.ttcautomotive.com/English/onlineorder/product.asp to download a FREE service manual for T5 or Tremec 3550
You will need the Adobe Acrobat viewer which is also a free download –
http://www.adobe.com/products/acrobat/readstep2.html
See
http://www.ddperformance.com/index2.htm for parts
OR
http://www.hanlonmotorsports.com/
A T5 rebuild kit with syncros, bearings and other small parts costs about $160. It does not include any gears or shafts.
The Tremec rebuild kit I bought was $384, it included syncros and all the bearings. There were no shims in the kit, and you will need them to assemble the trans with proper preload on the roller bearings for the main shaft and countershaft.
There is a video on how to rebuild your T5 or Tremec. If
http://www.hanlonmotorsports.com/ are out of stock see
http://cartapes.com. It costs less than $20, and is worth every penny of it.
I did a Tremec 3550 rebuild, and it wasn't that difficult. The video was an immense help, and I would recommend viewing it. At $20, it will give you an opportunity to look and decide for yourself if you think that it is something you want to try to do.