OP seems like a genuine guy, just new to this. OP I suggest you search the forum for other adds which received many upvotes to understand the type of pictures the community cares about (glass off and document any scratches, dirt, cracks on the play field, backless and cabinet).
Also search for previous whitewater ads to understand the price it fetched and why.
Typically unless you do your own cleaning and maintenance -- and if you are new it will be tough -- it's tough to justify the cost of having a professional do it. Although it IS far less hassle in selling the game as you're experiencing