Amp Question

Look we just finished are customers car and he brought us a used amp and said that it just came out of the shop.  Well we hook the amp up and when you touch the amp you get a little shock so, I put the meter on and I am getting 1volt across the ground and when I test the case and the amp its self is getting 1volt.  So, we belive that when he took it to the shop they did not do something right.  Also, when the car turns on the subs pop and I believe the amp is causeing that problem because the 4ch amp has no pop and it has 0re at the ground and I would like to know if amp could be the problem.  I hate to hook up stuff we did not buy or is not new because you run into these problems it seem.  What do you guys think we should do.  The guy had been nothing but, problems the whole time and I just want him to get it fixed and leave us alone we are to busy to be working on either hot or bad components you know.  And imput will be great.

Thanks

"Sorry man, your amplifier is messed up.  We can charge you $xxx an hour to try to continue looking at it, but we really can't spend any more free-time trouble-shooting this problem.  We don't really do amplifier repair.  Here's the number (xxx-xxx-xxxx) of someone that does do amplifier repair.  If you don't want to try them, I think you should contact the manufacturer again.  I'm sorry we can't help you more, but we have a lot of other customers waiting on installs and need to be fair to everyone here."

How's that?