Here is a great video of a T5 tear down. It gets you a little dizzy from all the little parts in it. I have a spare T5 and I might take a stab at it one day.
How hard are these parts to change? Something a run of the mill mechanic can do? Or need a transmission specialist? All i have around here is basic mechanics for the most part...and any idea of how long? Just so i can get an idea of total cost ...would prob do this over the winter and drop the trans off...be a good time to crawl under the car and prep/paint the undercarriage (which sounds like so much fun i can hardly wait lol)
I used to do it for $150 labor. It's honestly not that hard. It's a little tedious, but nothing complicated. People are terrified of fixing manual transmissions, and I don't know why. I never watched any of those videos, not that I am saying they aren't good resources. Figured it all out years ago with the rebuild manual. Which by the way, is a free download in pdf on the TTC website. It has blow up diagrams with all the part numbers too. The only really expensive gear set is the gear 5. I have hardly ever bought new non wear parts for a T5. Hang around on ebay, and you used parts are everywhere. The Cobra transmission was pretty bad inside and needed a bunch of stuff, including a new 5th gear set. The number 5 blocker ring had cracked years ago. Too many years of grinding it had smoked the engagement teeth on the gear itself. I got everything for $168 on ebay. Almost all of it was from one seller that had parted out a T5 he got from a V6 Mustang in salvage. It was all like new.
When you put it back together, use Ultra Black RTV. That's what everyone uses. Check the gears from scuffing on the teeth. With a lot of torque, the pressure between the teeth forces the fluid out, and it's metal on metal time. 93' and up T5 transmissions just use ATF from the factory. With that much power, step up to a more viscous fluid, like Syncromesh.