Definitely seems sketch, but wait out the 2 days, if he shows you another excuse instead of a title, bail.
Any leakage at all from a shock is bad news, but first you should absolutely rule out the possibility of it being on there as a result of spray from driving over some oil on the road, do you best to clean off the shock so it's dry and clean then drive the car on a rough-ish road on a dry day, then check again a few hours later, if there is any signs of oil again then you definitely have a leak.
As for a replacement, replacing just one would be cheaper, but you can get a full set on ebay for sub $400,
Cheaper but a bit rusty:
http://www.ebay.com/itm/Mitsubishi-...sion-Evolution-10-Oem-2008-2014-/192017228466
More expensive but cleaner:
http://www.ebay.com/itm/2008-08-MIT...TRUTS-SPRINGS-SET-EVOX-CZ4A-337-/281332210434
Your best bet would be to join an evo specific forum and ask about buying your particular required strut, as there will be plenty of people parting out crashed vehicles or selling their OEM shocks after installing coilovers/aftermarket struts, may even find yourself with a good condition replacement strut for under $60 shipped.