Can you replace a Cont 0-200 with a Lycoming 0-235 on a Cessna 150J would there be any problems advantages or disadvantages with this change overall?

the cont 0-200 has a better fuel consumption rate. Check with your IA and he can tell you if that particular combination is an approved installation It is an approved installation; an Airframe and Powerplant shop files a Supplemental Type Certificate, the FAA signs off on it (the O-235 was used in the Cessna 152 so there's no real problem with the conversion) and the mechanic inserts the new engine in your classic airplane. One quick note: Lycoming is not shy about pricing its parts.