Will a 1993 GMC Yukon motor fit in a 1998 Chevy tahoe?

Meaning - you could swap the hard part (engine) down to the block and heads, but even if all the 1998 electronics and sensors fit on the 1993 engine, you will inevitably find some problems with electronics compatibility. Also, you didn't mention if it was a like-for-like engine size, but even like engine sizes over a 5 year span have significant internal differences, such as valve porting, casting differences, intake manifold differences, bottom end of the engine differences, oil pump differences, etc etc... Also, a 1993 engine is OBDI and a 1998 engine is OBDII managed. Again, you could swap all the like sensors over to the old model engine going in, but you will almost certainly run into trouble.