Gah, what a bummer! Unfortunately these heads are super sensitive to valve adjustment, and I think most cars have been ignored for a good part of their lives. You may want to do a leak-down to confirm the source of the low compression before diving in, but they are the likely candidate on this motor.

If you are going to do it, there is a lot of auxiliary work that should be done at the same time unless you have rock-solid proof that it was otherwise done recently. That's what makes it get pricey. You should do the timing chain ($60+), guide rails (cheap-ish) and tensioner (and it's own guide - ~$200 - this is an updated part and must be done if it hasn't been done already), timing chain sprockets if things are badly worn ($350+ each!), head gasket ($150). Then you still have to deal with the head. Valves and seats should be ground and/or replaced. $300-$500 to the machine shop. Exhaust valves bear the brunt of the wear, and of course those are spendy - $100 each and hard to find. Couple hundred bucks for valve guides. Presumably you'll need at least a selection of shims to get valve clearance right.

As you can see, it adds up. You might want to consider a used head - there is one on 190rev right now, fully rebuilt for about the cost of a set of exhaust valves...