currently we have a old jennair wall oven. I didn't realize when we bought the house how small it was inside. I'm thinking of replacing the wall oven, maybe putting in a microwave and where the cooktop is, currently with a cabinet underneath, putting in a range. Would like the cabinets refaced so everything would match. another reason for moving the oven is that there is no landing space for removing hot items from the oven. Is this a good idea and how hard/expensive would it be (more than just replacing the units)

Without out at least a picture not sure how anyone could even suggest anything.
As far a prices that not likly to get you more then some wild guesses on the internet.
Going to have to make some calls to some local cabinet shops to get pricing.

Worth doing though. You'll free up all that space where the oven is now - like you say, could hold the microwave, or a pantry, or just open up the space. You'll also find that pricing for a range is much cheaper than that of a cooktop and wall oven - much cheaper.