Leaking tanks are very discouraging. I think if I were in your situation, the first thing I'd try is to use Kreem in the tanks. I helped my neighbor Kreem his tanks while still installed in the wings. It was awkward but it worked. You can buy Kreem online. Youtube has many videos to watch.

http://www.youtube.com/watch?v=dT3vUX7vUGs

This may be the cheapest way out initially.

I'm about to Kreem a pair of tanks in my current project. This might work out a little easier since these aren't installed in the wing yet.

Good Luck!