New to VFR world and new VFR owner

Being as how the inside of the tanks are not sealed to begin with I would say not necessarily. Depending on how good of a job the chemical he used to remove the rust does, he may be ok just keeping fresh fuel in her and gettin down the road. I would say that sealing the inside of the tank is a great preventative measure as long as you use the good/correct kit. There are newer kits out now that are resistant to ethanol which is now at 10% nearly everywhere in all gasoline. Older kits/chemical sealers were not designed with this in mind and can/probably will melt off the inside of the tank and clog EVERYTHING.