Even though you'd want another shop's ideas, you're still facing the basic question you posed. I'm certainly no expert, but I'd work from these assumptions:
1) You'll never get out all the money you spend on a total respray.
2) The car will sell faster and for a better price if it looks fresh.
3) The car-literate buyer will be reassured to see photos of what damage there was that led to the job, so he can tell it wasn't a complete Bondo-over-the-rust-powder situation.
'97 SL500, 40th anniversary edition
'04 Olds Bravada (SWMBO's)
'06 Lexus ES330
'89 560SL (sold)
SL--Anything else is just a Mercedes.
(Kudos to whoever said it first)