I see no reason why you can't as long as the rails are the same. You will have some spare parts just in case.

Hi Don,
Thanks for the answer.
I replaced the motor unit, and everything worked well, just had to replace the outdoor pad, and the car units. The sensors and indoor pad worked w/the new unit.

Can anyone suggest the type of greas to use for the plastic gear/belt?

The grease that comes with new gears is called Lubriplate. I'm pretty sure you can buy it at Home Depot in the garage door opener area.