Bit difficult to do these bits from the instructions with a built in tank.
9. Tip the tank onto each side and slosh the coating around to completely cover the inside. Use a rock-ing motion rather than shaking. It is important to do a thorough job or you may miss parts of the tank behind baffles.
10. Drain out the excess coating and cover tightly to save for reuse. The best method is to stand the tank up with a corner drain hole over a can to collect the excess as it drips out. It is very important that you do not leave puddles in the tank.
As dirk said, your tank may be baffled, which rules out a bladder, but if its not cutting a small hole is less surgery than taking it out completely, however remember not to use power tools anywhere near it
If you can get the fuel sender out, a careful prod around with a stick and careful inspection with a torch should show up any baffles.
Do you have a jockey seat over the top of the tank? as the hole could be cut inside that to hide it.