Transmission help

[landarts]

I finally finished up my long build enough to drive it . The build was over a eight year period. Before I tore the truck down it was a daily driver that ran well and had no mechanical issues, 350 v8 motor with a TH350 transmission. It would from time to time have a small drip or two of transmission fluid as well as engine oil. When I finally got it back together and on the road it leaks transmission oil about 18" x 18" puddle.

Here are the items I noticed after the first drive out of the neighborhood. The truck would not shift out of first gear. Went back home and drained all the transmission fluid and replaced the oil, filter, modulator, also replaced the vacuum line. The truck now shifts into all gears but it shifts really late. It has to get to high rpm's before it will shift. For example where it used to shift around 20 mph now has to go to 35 mph with high rpm's.

So the two problems with the TH350 are it is shifting late and is leaking badly. Does this need to be rebuilt? Is this something a first timer can do? Please advise, and thanks in advance.