Is it possible to rebuild yourself at home

Yes. Take pics.
Use a small bottle jack & chain to pull out the oil pump. There are several wire type snap rings one needs to remove, be sure you have two scribes, one to pull out, the other to block and work the two together to remove the rings.

When you get to the bottom, the low/reverse reaction housing, there is a clip at the 5 o'clock position. DON'T FORGET this clip upon reassembly, trans will not move without it. Take picture of it installed so you can reinstall it correctly.

You might find a book at your local trans parts shop and buy the manual, printed by ATF Group, or try www.Amazon.com Read the book several times.

When assembling, use a large rubber band to hold the sprags in place when assembling outer race. You'll see it right after you remove the oil pump. Get a hardened outer race, can't hurt.

There are more tricks, others here might expunge their knowledge.

I bought an instructional video on rebuilding a TH350. Very detailed. Cost about $30. I have rebuilt 2 TH350s so far and they are holding up fine. A book by Ron Sessions on tranny rebuilt was a nice extra material (a lot of tips and pictures).

Regards!
Den