91' Cadillac Deville GM say's it's not worth fixing

My number 5 valve is missfiring, it failed a compression test it tested at 100 psi they said it's probably a bad oil ring or something. It has 226k on it would it be worth it to tear this engine apart and rebuild it? I really want to fix this car up possibly to pass down to a younger sibling. I just found out one of my friends has a guy that will rebuild my engine cheap, how much would a cheap engine rebuild cost me?

Thanks for any help in advance