I would budget $2k, interview 2-3 designers.

The devil is in the details, the more details, the higher the design costs.

A contractor may grunt at you during design discussions, and you may or may not get your vision.

For a bath that small we would probably charge around $500.00. But, it really depends on location and the amount of work involved. Expect a higher cost on both coasts and in big cities.

I also struggled with trying to figure out how to work with a designer, how to hire a designer, what I should expect to pay, what questions to ask, and just generally how this whole design business works. I went onto the NKBA website and another one that I think was called ASID. Try going on those websites and finding a certified kitchen and bath designer. You can pay for a one time consultation of about 90 minutes for maybe $250. That way you can consult with a professional and try to figure out how much more help you need. Some homeowners only need a few consultations, but other homeowners need a designer to take over the whole project. If you have the initial consultation you might be able to gauge what level of help you need