...my car has been sitting for awhile, a year or so...lots of oil coming from the return tubes. Can the tubes be repaired or better, replaced without removing the engine? Is this a big job? Thanks for your thoughts...

return tubes ... would that be a /6?

either way, the /6 return tubes as well as the /4 pushrod tubes can be done with the engine in the car.
Andy

You mean the pushrod tube seals?

Yes, the seals can be replaced without removing the engine. You will have to pull the valve covers off, remove the rocker assemblies and the pushrods. When you've got the new seals on and are ready to re-install, be very careful not to get any gunk or debris on the seals -- could cause another leak.

And it might be a good idea to drain the oil first.

Thanks!