WELL, I'M OUT. . . . . . . . . .

[chumbucket]

I believe you should have the trim tab one, one on each side of the gimble mounting bolts, and one at the base of the gimble. I've even seen people use the clamp on style on each trim cylinder as well.
Yes, the trim cylinders can be rebuilt depending on the amount of corrosion.
If you're in a marina that you suspect to have a lot of stray electrical current in the water, use an external sacrificial zinc anode dangled over the side of your boat.
Like this;
http://www.boatersworld.com/product/327250254.htm