1) would a full colour change have a catastrophic effect on the resale value?
Depends on what it is, but generally no, although a vinyl wrap can be hiding unknown damage underneath as you never know what its like till you remove it, which can put some buyers off. if your looking at a full paint job then its about £2k for exterior only and near 4K if you have all the engine bay and door shuts done etc.
2) might a smart repair job on these marks, followed by a vinyl wrap be a better idea?
Not a bad idea, but a vinyl wrap can lift smart repairs when you reomve thevinyl if your not careful.
3) how long does a wrap last if you take care of it?
How longs a piece of string; depends on the vinyl who fitted it, how its cared for,, what the weathers like. there are some new finishes out there that are good for 10 years. i'm looking into some stuff from the states but its not cheap
4) any other suggestions on tackling these that I haven't thought of?
no
5) is it legal to shoot seagulls if they cr@p on your car?
yes