To replace the head gasket, you have to remove the head from the engine block.
Virtually the whole cost of the process is labor. How much is the gasket set - 40$??
You can always replace the valve seals with the head on, but you can only replace the valve guides with the head off.
Since you have to remove the head to replace the gasket, spend the extra $200 or so and replace the guides and seals.
You'll then be good for another 250,000 miles. The new guides and seals are better than the originals.
2001 E430, Bourdeaux Red, Oyster interior.
1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".