Rotten eggs is from the catalytic converters, you're not burning up transmission or engine oil, nor coolant. I have smelled that a couple times from my 1998 Mystique. Is the 50 km the long hill? If not, you will probably make it. As a test let your car idle till the M on normal is reached and the radiator cooling fans come on, the temp should then drop, that verifies the engine is not overheating. If OK, then take a drive, put in park, check trans fluid level see if it's ok, and not burnt smelling or brown. There is a sharp smell and red color to the trans fluid normally. The engine radiator cools the trans as well, so making sure the engine cooing is OK relates to the transmission.
