suburban water heater leak

I have a couple of ?'s. I removed my tank and it was rusted right at the drain out plug underneath. From the looks of the damage to the floor is sub structure, it has been leaking from the previous owner. Anyways, I repaired sub structure and floor to the best of my ability and cut out all rotten wood that i could see. I stop tearing anything past a 2 x 4 ft area as it looked like most of my damage was concetrated at the right rear corner. I have since gotten a new suburban tank, only because everything was fit for that tank. I am looking for the rubber sealant they used around the propane line connecting to the burn assembly. I also have some dicor tape sealant for the door frame but can not find the rubber back type of sealant. I then got some 4 x 8 plastic mobile home underside tape to fix the tarp where I cut it. Is there anything else that i might need. I do know that I will have some reservations on sub structure being that I am not completely sure i got it all. But at what point do you call it quits.

thanks

mike