This would be a piece of cake. Just put out some steelramps to land a sublift on. Ferry and drive it to the boat, lift her gradually in the sublift and drive her back to deep water...
Maybe there are no such high capacity sublifts available yet, but it can not be too hard to build within a month or two...?
Here are PDF-drawings on a 300-tonnes from Anytec in Sweden.
http://www.anytec.se/filarkiv/GA-1300.pdf