Repair man came out and told us that the drum needed to be replaced in our copier, a Minolta EP 5000. That info cost $150. Then he said the drum itself was $450 and then it would be another $150 to come & install it. Yikes! 750. I find the part online for 150. Would like to install myself if possible. This copier is used in a church (non-profit) for our Sunday school mainly. Issues are 2: first, $750 is out of our price range; and second, don't want to put yet another huge piece of equipment needlessly into a landfill. Is it possible that this is a diy project? Where can I get printed instructions?

Not a very honorable company in my opinion. You're right, a generic drum is much cheaper, and will perform fine, but replacement is unfortunately not possible for a non tech. There is a drum cleaning blade that needs to be installed with it (inexpensive and included in his quote I would hope/ assume), and then certain calibrations and adjustments need to done. -all of which should be easily accomplished for far less than the $450. I know it would be if I were doing it. (You're not in the Toronto area by any chance?)
I would call another company, and tell them that you require this to be done and find out how much, before bringing them in.