Switch out oven in favor of Microwave

I briefly searched and could not find the answer to my question so hear goes... I walked through a new TM a couple weeks ago and the dealer had a microwave installed instead of the oven. I don't see myself using the oven much (tell me if you use yours a ton so I know I am wrong here...) but I can see using the microwave). So, given I can't afford the new TM and we are looking used and many of the used ones have ovens with countertop microwaves, I am wondering as a weight saving technique how hard it would be to remove the oven and put in a microwave instead and would I have to get a special microwave?