What can be done to a T5 without replacing it?

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.

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.

You will also need a magnetic base and dial indicator to measure the endplay ($20-$40). See http://www.mscdirect.com/PDF.process?pdf=1312&Keyword=Y