Filling tires on my 790

I have a friend who has a the machine to fill with. I can get a 55 gallon drum of methonal for $250, he said if I buy that he will fill the tires at no extra cost if he can keep the unused of the methonal. Is that a good deal? What about filling the front tires too, any benefit from that? He said there are likely tubes in the back tires, is that true?

I have the AG tires if that makes a difference.