How to and how long to change an alternator

Depends on the year. The late 90s Cutlass Supremes with the 3.4 have the alternator tucked up from underneath in a very difficult to get at location. Changeout time is 3-5 hours depending on your skill level and tools. It will vary from year to year though and for different engines.

i got so i could do it in about 2 hours out in the snowbank ...but i did 5 in a row..finally put a lower amp one on to cause it heated a little less

Yes, That would help you get good at it all right. When I did mine I spent about half the time figuring out where the bolts were and how to get at them. Knowing that its actually not that difficult. Thankfully mine isn't overheating like yours was so I expect it to last for the rest of the car's life.