Transmission

It really depends on what your goals are for the car and how much money you are willing to spend.

There are numerous ways to go right now, not 1 being the only way.

It also depends on your mechanical ability. If you feel comfortable doing this type of a job then I say go for it. It is not really that hard to do.

If you don't feel comfortable doing it then leave it to someone else.

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.hanlonmotorsports.com/ or http://www.ddperformance.com/index2.htm for parts

A T5 rebuild kit with syncros, bearings and other small parts costs about $160. It does not include any gears or shafts.

http://cartapes.com also has a video on how to rebuild your T5 or Tremec. 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.

If auto, get an AOD if you have mods or plan on doing some. I would go to a Tremec 5-speed. I still have the stock T-5 in mine with nearly 400RWHP and she's still holding up...granted my car has 87k on it.