For three years in a row, we chartered with Moorings (Greece, Martinique and BVI). For each of those trips, we took a skipper on board for a couple of days.
1/ All of the experiences were excellent, the skippers were very helpful, and had excellent knowledge of the boat, the sailing areas and dos/donts.
2/ For each of the cruises, we only took a skipper on board for a couple of days to a week, to get us acquainted with the ship and sailing area, after that, we continued on our own... I found, if you know how to sail a boat but are uncomfortable about the first couple of days, it is a good idea to take a skipper onboard.
3/ A must for the privacy, is to ensure the skipper has his/her own cabin.
4/ We always invited the skipper to join us for meals onboard or on shore. While onshore, we paid for his meals.
5/ The skippers were always very sensitive to our privacy, and often suggested we dropped them onshore for a while (while at anchorage), so we could have some time by ourselves.
6/ Keep your eyes open 'for the signs', though... Our last skipper came on board with a couple of sixpacks of beer. The first day, he took his first beer at 1 pm, the next day at 9:30 AM (!)... We had a similar experience when chartering for a training cruise in the UK... There the skipper often tried to convince us to go into a port before 3 pm, later only to find out that 'he liked his drink'.. These were all minor problems though. They never got drunk on the boat (but then again, we never had a skipper onboard for more than one week...).
7/ make CLEAR agreement the first day as to what you will pay for him/her (meals, drinks etc..), and how... Last charter we suggested the skipper ate with us and said 'our fridge is open for anything you want'.. He always refused, and hardly ate anything. Back on shore, through the charter company, he later tried to claim $150/day of provision fees...
Overall: don't worry.. you will be fine.