Are you set up to pull the engine?
Allow 2 days to disconnect and pull the engine. Allow the same to drop it back in.
If you've got solid help, or done lots of engine in/out you can probably do it quicker. For the shade tree guy, there's a lot to disconnect, clean, organise, fix and...
Let the car coast down a long hill, punch the throttle at the bottom.
If it puffs smoke when you punch it, most likely valve seals.
My money is on valve seals anyway. Given the age and heat/cold cycles, they'll be rock hard and doing nothing.
I was also using quite a bit of oil before changing...