Welcome aboard Dave. I put you in your own post as opposed to hijacking the other one :nono: Take a few and review our FORUM RULES, if you would.
There's not going to be a parts manual for the boat. They didn't really do that for boats. Most gauges were considered "rigging" anyway and are not specific to your boat. In other words, you can kinda' do what you want to with 'em.
Your chances of finding the entire cluster are rather slim but one place to check is greatlakesskipper.com. The housing the instruments were mounted in may be unique to the boat so the boat manufacturer is a possible source but after 23 years it is highly unlikely they would have one in stock. Gauges are gauges -- they are very generic and available everywhere including right here on IBoats.