if I were you I would take your vin to gm and get a price on one of their rebuilt units. mot sure about USA, but GM Canada warrantees theirs for a year and you get the proper trans for your computer. I have heard some horror stories about diy 4l60e rebuilds. lots of money spent that went out the window upon start up, or a week later or whatever.
one more thing, if your trans is toast, don't forget to flush the cooler lines and include the price of a good inline fluid filter, or just flush the lines,change the rad and be done. otherwise all that crap that came out of your old trans and lodged itself in the cooler lines and cooler will come back into your nice new trans and take it out prematurely. you can't flush one of those "in the rad" coolers once they have particles in them don't reuse them without at least a filter inline on the return line.