if you think you can do it yourself and if it's a good enough price, go for it.
but if you're just going to give it to your local mechanic, i wouldn't grab it. that is, unless, you're getting it REALLY cheap and the rest of the ride is nice.
the gasket itself is really cheap. you can get them anywhere from 10-50 bucks depending on the model you need.
the labour though, is EXPENSIVE. the head has to be removed from the block and sometimes there's a lot to go through before you can just remove the head itself.
on top of that, if the head or the main block is cracked, that's trouble. it can essentially mean a complete re-build is required.
another problem you might encounter is that the head might have gotten warped. depending on what it's made of and how long the broken gasket has been driven, the head unevenly vibrates against the engine block. in cases where aluminum heads are used, they have to be machined smooth before they can be placed back on top of the block. this costs a lot of money to have done for you.
but again, if you're getting a good enough deal, GO FOR IT. and let us know how it went!!
good luck!