A survey is a must and you should ask around for recommendations for someone knowledgeable and reliable. The fee shouldn't be your first consideration.
I had a survey done on my "new to me" boat in late November by Al Prisco after several people here recommended him. He was fantastic and worth every penny.
I'm by no means a surveyor or expert marine mechanic but I am pretty thorough, mechanically handy, fairly knowledgeable about boats in general, and very very fussy. I looked at a lot of boats over the period of about a year before deciding on this 410.
I went over this boat with a fine tooth comb and drove the salesman a little nuts. I spent a couple of hours going over the boat myself before agreeing on a price that was subject to survey and sea trial.
My own inspection led to a list of fairly minor things for the dealer to address as a condition of sale before we agreed on the price, and as thorough and picky as I am Al came up with two more items when he inspected the hull that I wouldn't have.
Both were added to the list as a condition of sale. The salesman and his manager pushed back on both of the items initially arguing that I was going too far, but they were present when he did his inspection and they really couldn't argue with his expertise and recommendations.
The two things he came up with, which by the way the dealer ultimately agreed to do as part of the sale, would have cost me more than what I paid for his fee if I had to pay to have them done down the road.
He also answered a ton of questions during the survey/sea trial that I had come up with as a result of my own inspection. I probably drove him a little nuts too. It was a long day from start to finish and most of the survey was done in a torrential rain storm. He really earned his fee that day.
Once the lab results came back on the fluid samples he took and he completed his report he spent more time going over everything with me and answering even more of my questions.