I had a T4 in my 83 CJ7 when I got it, the syncros were out and I wanted to upgrade to a T5, bolt up application. I bought my 258 at a wrecking yard for 650, it came out of a CJ8 that recieved a 350, only had 59k on it. I asked the guy if they rebuilt transmissions. I traded in my T4 for a T5. They used my case, new main shaft and anything that had been ground during shifting was replaced. All new bearings and syncros. They bolted the overdrive housing to the front and I gave them 650. I priced the parts in a catalog one time, it was going to cost me more in parts to fix it myself then it would have to have the guys that did mine to fix it. I guess it doesn't always pay to do it yourself.
I rebuilt the T4 in my S-10, it was really a cake walk once I stoped trying to follow the instructions in the Chiltons manual step by step. (the instructions in my Jeep's Chilton's were worse!) A T5 is not much different.
Just use the instructions in the manual as a general guide so you know the order of dissasembly. Do pay close attention to the special instructions like matchmarking the front bearing retainer to the case (it can go on 4 different ways, but only one is right)
Invest in a polaroid camera. Take pictures as you dissasemble the trany, it will help.
Get a large clean work area so you can lay all the parts out within reach, in order, and not have to move them untill you are ready to put them back in the case. A 4x8 sheet of plywood set on top of two sawhorses is just about perfect.
Send the wife and kids to Grandma's house for the duration of the rebuild. I have no idea what a three-year-old thinks an input shaft is, but it must be the most wonderfull toy on the planed because I had to retrieve mine from the toy box at least three times in two days.
The only special tools you will need are a pair of snapring pliers, a vice, a small prybar, a set of pin punches, and someting to drive the bearings into the case. I use som old sections of steel pipe.