a naive new resident like myself might wonder if the directors were being suspected of trying to get their hands in the public till to obtain thousands of dollars of personal benefits for themselves, friends, or political supporters.

Not sure how anyone could possibly come to that conclusion. No one has even remotely suggested anything of that nature.

How are the lucky few dock renters selected?

Put your name on the waiting list. Since there are already 100 names on the list, the new marina, with 54 or so new slips, will reduce that list by half. The new marina slips are spoken for before any construction starts. Then we can start figuring out how to accomodate the 2000 or so Ocean Piners Bob Abele's committee believe want slips.

Is there any limit on the length of time a renter can continue to use a slip before relinquishing it to someone on a waiting list?

Till death or divorce us do part.

Does anyone have even the foggiest idea of the portion of the sales price of a house that might be attributed to the existence of an HOA-owned marina?

Zero.