Can I install an over the range microwave (or get someone to do it if I can't lol) even if there was not one there before? Or does the building have to be 'ready' for it somehow?

Is there an outlet there or nearby, assuming it's a microwave with a plug?
Then sure, put it above the range.
(I wouldn't do it - then you have the problem of dealing with cleaning the underside of the shelf or installing a vent/grease trap. I'm too short anyway.)

Lol yeah I'm short too but hubbie is 6'3 :P

Good, so hubby gets to clean it.

Hahah absolutely :P

I may not go that route anyway. It would certainly be nice to have. But so much easier and cheaper to just go with a counter top one.

I love to watch home improvement shows, and I love counter space as much as the next cook. I know clutter is out and I'm all for that. I don't even have a very big kitchen, 8'6" x 11'. But I see all these microwaves either high up or under counters these days, and I don't get it. Even the owners sort of mumble 'yeah it's tough bending down' or 'yeah I can't see up that high' yet they do it anyway.