Replacement is a PITA because it requires the plenum and lower manifold pull as well as the timing belt. Consider a bypass for the det sensor, Search for that procedure. There are kits available from TTers on this site. As far as the smoke if it smells sweet it is coolant, bad sign. Have the cooling system pressure tested.
How many miles on the car? What service done? Was the timing belt service done?
You should have had the car checked out by someone familiar with Z32 because even for the cheap can get expensive with required repaires.