There is a difference for sure. The front wheel bearing can only be bought as part of the hub assembly. The 89-90's are EXPENSIVE since the only car that had ABS those years was the SC. I suggest buying new front rotors 91-92 and hubs and swapping them all since you can get the hubs for those years and rotors for less than you would spend on just the hubs for the 89-90.
Don't forget new hub retaining nuts as well since they are single use items. No need for having your wheels fall off. They also need to be torqued to like 250 Ft-Lbs if memory serves.
The difference in the hub assemblies is the diameter of the ridge that "holds" the rotor inplace. It is a raised area circular just outside of the opening for the reataining nut. If you change to the later model rotors with the hubs the hole diameter matches and it all works out fine. Other than that I know of no differences. Make sure of course you select hubs with the ABS Sensor rings.
Nope...all you need to do to my knowledge is to change the Hub Assemblies installed with new Hub Retaining Nuts and install the new rotors. The calipers should work fine. Might want to change pads at the same time though since you are installing the new rotors.