all, depends on how bad it, and the rest of the seats look... the head will obviously have to come off, so that in itself says to send it to the machine shop and let em go over it as needed.... and if you decide to send the one head out, it is usually advisable to just do the pair of heads to keep things even..
but in a pinch, you can sometimes get away with just lapping the valve in question with that head off... it could be a bent or sticking valve, but with it making compression, than losing it, indicates a seat issue..