old Honda power washer question (update)

Need some advice on a power washer my dad bought in the mid-1980s that I now have. It's a Honda GX 140 5 hp generator on wheels with a Landa T911GR pump attached. Setup looks similar to this image (not the exact model):
We used the hell out of it back in the day, was well-maintained, but my best guess is that it's been sitting, unused, unstarted over at least the past 10 years. Other than being very dirty it appears to be in good condition.

Question I have is, should I change the oil, check the air filter, gas it up and try to start it? Or bring it to a small engine shop for them to check it out. I wouldn't want to do anything to damage the unit and my proficiency with engine maintenance is pretty limited. Also, if you have any recommendations for shops in the N.O. area, would appreciate that. I used East Bank Cyclery to repair generator last year and was happy with their work. TIA

Update: I replaced the carburetor and the spark plug and she cranked right up. I found the old carburetor was rusted and spark plug filthy/burned end. Thanks all for the advice.

I do have a question. After starting, when I opened the choke the engine seemed to revv too much and was very loud. I didn't run it very long as it was raining yesterday. Could that be due to it sitting for years and I should let it run some more? Perhaps replace the muffler?

Thanks in advance.