C6 rebuild

Long story short I was boppin down the road and it was like it kicked into neutral. I lost 1st,2nd and 3rd. I still I have reverse but I’m assuming that’s a whole different clutch pack. I’ve done some mechanic work before on engines and what not but I’ve never dug deep into to transmissions. My question to you all here is how hard would it be to rebuild it myself? Not sure of the year of the transmission I know they were produced from the mid 60s to about 2005 according to Wikipedia. Any help would be greatly appreciated