GMC Repair: 1993 Buick Skylark belt tensioner assembly, buick skylark, belt tensioner

Question
Trying to stay ahead on repairs of this old car I find now I need a belt tensioner assembly.Would a young person who might attempt to replace this be more of a risk than having a specialized mechanic to do the job? The cost I have been quoted is $270 and is that fair? Also, it sounds like a ball bearing rattling around. Waiting for funds to accumulate how will I know to bring in immediately? (yes, I am also aware that when it goes it means more repairs)
Thanks.
Buick Skylar, 111,000, 6 cylinder grand sport I believe.

Answer
The belt tensioner is not a hard job.  You should be able to just take off the serpentine belt, then unbolt the tensioner and put the new one on.  If I were you I would try it, even as an amateur. The 270.00 price is mostly the shop's hourly rate which is enough to make you a millionaire if you earned it full time.  It's a non-intrusive simple job that I would try if I were you.  If you were in my area I would do the job for half of the quote you got, easily.