The dealer should top it up for free under the warranty. My 335xi oil level never really moves, even though I do see a slight puff of smoke on start up. Oil consumption may not be an issue, but it really depends on the rate of usage.
With regards to maintenance, I wouldn't follow the maintenance schedule since my car recommends oil changes every 30k; I do an extra change in-between. Someone on this board bought a used X3 with about 50k on it with significant sludge in the engine.