'97 Chevy Tahoe with electrical and transmission issues

"I have a 1997 Chevy Tahoe I bought it about 3-4 months ago when I bought it, it had been in an accident and had some work done I don’t know what work. About a month after I bought it the transmission died. I finally got a used transmission put in about a week ago by some friends now it is having a hard time shifting it revs up the RPMs and shifts but the RPMs stay really high unless I go under 30. Not only does it have the hard time shifting but if I let it sit for a couple of days the new battery I put in it is dead and I have to jumpstart it. It has had a few electrical issues since I got it the gas gauge bounces around and the windshield wipers are sometimes really slow and sometimes normal. Can you please help?