Broke a faucet handle... Replace handle or faucet?

You didn't say if it's a kitchen or bath faucet, but both can typically be replaced with standard items from one of the big box stores. The actual R&R is no different than doing a residential fitting in most cases. If you've never changed a residential faucet either, then as said, calling in pro may be your best bet. As the saying goes for RV ownership, "Handy with tools, handy with your wallet, take your pick."