My quest has brought me to yet another airhead, a 1978 R100. Bone stock except for the Dyna III ignition. No bags, fairing or windshield.

... second owner, 15,700 miles. The bike gets about 60 miles a year for the past 5 years.

The Good:

Fires right up.instantly! (after charging the dead battery)
No smoke
Rides and shifts good.
Clutch good
Brakes are good
Cosmetically 7/10
Tank lining good
Never crashed
All lights/electrics work
No dents or dings in the rims
Cables operate smoothly

The Bad:

All 4 push rod tube seals leak bad.
It may have leaky front and rear main seals too. There is oil at the front of the engine at the base of the front cover and rear in the trough area
There is oil weeping at the cylinder bases at the engine block, not leaking, just weeping.
Idles a bit rough under 2500 rpm but smoothes out above that (carb clean/rebuild?)
The mufflers are rotting from the inside out at the weld by the taper... the metal is expanded and obviously rotting
Tires are good but old and have to be replaced
Needs a battery
Steering head needs adjusting/tightening probably grease too
There are scratches and chips here and there but I think it will clean and polish up nice.

All in all it seems to have a lot of potential.

I am not a mechanic, but I do know what end of a screwdriver to hold...somewhat mechanically inclined and a lot more patient than I was when I was young.
That being said...
Are the main seal leak problems a major undertaking to fix? The engine is not oil soaked just greasy oily front, not as bad at the back.

Pushrod seal seem straight forward. I imagine its pull heads, pull jugs (with pistons still in or out?) remove tubes and seals, clean degrease everything, install new seals, reassemble with all new gaskets and torque, then re-torque after X miles.
Probably a good idea to de-carbon everything while its apart too.

What say you?