What diameter are they at the stump and how many? A tiny machine can do a big stump, but it will take a while and you'll spend more in hours. You'll want to size the machine appropriately.

A hydraulic thumb to help lift the stump out is nice. I'd ask if they have a "frost ripper" that you can rent in addition to a digging bucket for the machine. It can help avoid disturbing as much earth (look up "removing stump with frost ripper").

If this is an area you want to be grass, plan on how you are going to fill it. Stumps leave a big void.

I agree with the other poster that if you can wait a year or more they are easier to deal with.