First, don't put any sealer in the tank. If you do it will cause more problems than it will solve. The best but maybe not easiest on the IT series is to - drain the tank completely and don't start the engine after you do (the pump will hate you)- flush it out best you can without using solvents or fuels. I use a steam cleaner to get all the built up years of crud out, this is not easy but does a good job.
Get a patch plate made that will fit the area, a little extra time spent fitting will make the repair last. Make sure to go above the point of leakage to get to a good base for welding. If you aren't capable of running a good solid bead and restarting after a break or rod change, get someone who can. Make sure the area is well prepared ie ground clean with no paint or rust. After you are done welding and everything is cooled, paint well, we use to put a rubber flap over the area to keep this from happening.
