I just went hunting through my pictures because I spent a good amount of time with my head crammed into that space on our 282 last spring (trim tab pump rehab). No clear photos unfortunately. When you say your tank has a leak, is it leaking around one of the fittings through the top of the tank, or do you have some sort of other damage on the sides/bottom of the tank? It's hard to think of anything that could hurt the sides/bottom of that tank unless you had some sort of ice related rupture of the tank.
But assuming lifting the deck plate and the main fuel tank is out of the question (not even sure that would give you access), then I'd say you're either cutting up the tank and pulling out the pieces, or cutting a bulkhead to make more space.
I don't think you should make a decision based on your first rodeo with this. I'd recommend contacting the Grady White factory to see if they have work history/best practices to do that sort of job.
And sorry, that's an unfortunate task to tackle . . .