brentleedragon

I have a C1500 Suburban LS, it has a 4l60e in it,with 300,00 (same engine and same tranny) THe tranny now wont go into reverse, and to shift it from 1st to 2nd you have to get the rpms up to 2800 and then let off the gas and it shifts. It shifts fine from 2nd to 3rd and does not shift into 4th. My question is how hard is it to rebuild the transmission? Or is there something I can do to fix it (i dont think so from what I have beent old)

THanks