How much to replace a head on a 96?

I was looking at a 96 Roadmaster that's for sale in town. $1495, one owner, 136000 kms. Only problem is, it sounds like that valve guides or whatever problem the LT1's had is bad on the right head, and it's spewing a lot of bluish-black smoke from the right exhaust pipe. The salesman at the car lot told me he think's it's the lifters, but after some looking I think it's the exhaust valves. The salesman told me it would cost between 800-1500 to have the lifters replaced. Seems kinda high but what do I know. Assuming that the problem is actually caused by the valves and a head replacement is required, how much would this typically cost?

Did you notice if the engine heats up quickly? That could indicate a leaking head gasket or cracked head. It sounds like it may be in the bottom end i.e. rings, cracked piston, loose wrist pin. Pull the oil fill cap off while the engine is running and put your hand over the hole to see if you have vacuum or pressure. Lifters or exhaust valve would not cause it to blow black-blue smoke. That sounds like oil smoke!!