Is it hard to fix main seal between trans and engine?

if it is leaking trans fluid then the front pump seal is probably leaking , you will have to pull the tranny out to replace it and while you have it out you might as well check the rear main seal on the engine. !!!

I have replaced both seals from autozone and orileys and for some reason they do not last only for a few miles and it starts leaking again. Did you ever find a seal to last? I have heard you need to find a oem seal, original seal. Chevy does not have them. Can't use aftermarket ones.