Microwave for 2720SD

We feel like veterans after our trip in September, taking our TM through No Cal and Oregon! But one annoyance was the microwave (not installed, just sits on top of the microwave box)--the previous owner included the one that came with it when he bought the trailer from the first owner. It likely dates back to 2002 and has no real features, just a turn dial for the time.

But now that we've experienced the, ahem, wide variety of electrical hookups in campgrounds, I wanted to ask about microwave wattage before I buy a newer one.

Does it matter what the wattage is on the micro? Would it be wise to stay under 1000 watts, for example? Feeling like this is a stupid question, but it's better to ask before we learn something the hard way!

Thanks!