Smoking realy bad ithink that it is valve seats.do

As far as the smoking, first what color is the smoke. If it is whitish then it most likely is oil smoke. If it is blackish it is excessive fuel (rich mixture).
Does it smoke all of the time? If it smokes mostly on accelleration then most likely the rings are bad. This can be checked out by completing a compression test, first dry then wet.
If it smokes mostly on decelleration then it most likely is the valve guides.
A valve seat that has gone bad (burnt) would not cause the vehicle to smoke, it would cause the vehicle to miss.
Yes, you have to remove the heads to service the valves.