im deciding between an 07 infinity m45 or a jaguar s type R, but i want to know if infinity has a maintanence policy like bmw or mecedes (service A and service B), are parts expensive?, whats the difference between an m45 sport and just a m45? any expensive future wear and tear breakdown problems i should consider?

Go with the M45. The sport has a little stiffer suspensions and larger 19" wheels versus 18" wheels. Both will offer pretty good service (at least around here)