Hi Ben,
There are several bars and two nightclubs. There are also regular block parties and community events. It really depends on what you want from a nightlife.
San Pedro is not really a village but a small, booming little town. It has three main roads and a wide variety of shops, ranging from small holes in the wall selling local food and produce, to higher end shops selling imported goods and expensive alcohol. Again, it is all a matter of tastes. Groceries are generally expensive unless you are prepared to only purchase local goods and produce. Groceries are generally more expensive in San Pedro than they are in the USA. There are several doctors and a polyclinic on Ambergris Caye. The polyclinic does not offer over night stay facilities so you have to be transported to the mainland for medical emergencies. Should you want medical care superior to that provided in Belize, Merida and Guatemala City are popular choices.
There are other threads here about real estate companies. Do a search and you'll find loads of good advice and recommendations. My own advice is to visit several, get to know them and find one that suits your personality and style.
The best way to find out about what life is like in San Pedro is to try before you buy. Most people test drive a car before buying it and with an investment that is even bigger, like real estate, you really do need to get a feel of the place. 3-7 days is not even close to giving you a true perception.
The expats who seem to do the best are the ones that come with low expectations, a good cushion of money and spend several months to a year here before committing or buying property.
Ambergris Caye is a perfect fit for some people, but just like shoes, you may not find it fits at all.