I just did this on Penelope and luckily, the panel was removed. I could see having to pull the engine on an upright engine, but that should be pretty easy with a floor jack. I got mine out without removing the engine. I bought 2 gallons of muratic acid and a gallon of acetone. I also got eastwoods sealer for 29 bucks. Cleaned the gunk out with some acetone, rinse, and fill with diluted acid and water( do what you oughta, put your acid in the wata'- so it doesn't blow back on you). Rinse, clean with acetone to dry out the tank. I ran a hair dryer in it for a while till it's dry. Then follow the instructions on the tank sealer. Worked beautifully! If you have questions, ask.
use bolts or marbles as aggitators when breaking up gunk and rust