Pre-purchase advice

Hi all, I am new to CCF and forum.
I am considering the purchase of a '78 Correct Craft Mustang 17 with a Ford 302 - going to see it in a few hours ... the current owner has owned for 2 years. He replaced the interior, gauges and steering wheel and from the pics it all looks very nice. The exterior seems to be in great shape as well. He indicated that the cutless bearing is new. He said he has not anything to the motor other than change the oil as needed, and redid the carburetor.
This would be my first boat and I've been looking for something under $10k that I can just have fun with on the central fl chain of lakes with my kids wakeboarding, tubing, etc. The owner is asking $5k.
I am not really mechanically inclined so I would rely on a local mechanic for servicing, etc.

My main concerns are reliability - possibly getting in over my head with something that I can't afford to fix or update, and access to parts in the future if needed.   
A local mechanic told me to make the motor has a serial #, to test run it at 4600 rpm for at least 10 minutes, to check the oil and tran fluids for milkyness, and to make sure the temp stays under 160.
Assuming all this checks out today ...
Anyone been in the same boat before, or have any advice on making a wise choice?

Thank you for insights, I greatly appreciate it!

Since you are new to boats, I would take it to a marine shop for evaluation.     It might seem like extra money to spend, but in the long run you will be ahead.     It is 41 years old - it could be a money pit.

That’s not the Mustang the guys been struggling to sell on Rose Ave is it? When you say you’re trying to keep it under $10k, sounds like you have a $10k budget. I too would look for something a bit newer if you’re not mechanically inclined and familiar with boats. The difference between older boats and 90’s+ is rot. The rest is the same. There’s a few ok 90’s boats around right now in the $8k range. The GT40 is a great motor but honestly being 20+ years old, the electronics and moisture is getting to them so I would stick with a carburetor IMHO.

I have owned tournament Ski boats since 1982 and would never run one at 4,600 RPM for 10 minutes. Maybe 1 minute and then I back off. I am not willing to put that much strain on an engine for that long. Some might but I would not.
I think 1993 or 1994 was the year Ski Nautique eliminated wood from the stringers and replaced with fiberglass stringers.   These newer boats will never have rot, they ride better, turn better, are a little safer and have a better wake with more storage. I owned a 78 and now a 95, it was a very good upgrade.
If you happen to prefer the style of the older boat I understand that completely and would support your purchase.

I checked out the boat yesterday. Owner took us out for about a 30 minute ride. The boat is in very nice shape and seemed to run very well. We checked the fluids and they seemed fine. I am arranging for a mechanic to go back with me to do an inspection.