[tsubaki]

First determine if there is a fuel cell leak ,removing the boat from the water, if so, 5 gallons at the time are easily handled (hope you got a pickup). Just siphon (you'll be a pro after this) and save (unless it's not mixed with oil) for reinstallation. The cost of the 5 gallon tanks will be nothing compared to the work involved and later they will be apreciated.
There are not many boat mechanics in this area that will profess to doing this work in a cost efficient manner. I do my repairs myself and won't suggest any references, reasoning being, by the time a good mechanic is found at a shop, he has moved on somewhere else. Ask someone you know and trust to make a reference to do work.
There is no other boat that rides like these and handle as such, they are well worth the renovations (not monitarily but piece of mind) and endless labor of upkeep (as every boat is).
Let us know about progress (and pictures).