>>I have a Sunfish sailboat on a trailer-best place to sail it?
On the water?

Seriously, pretty much any body of water in the area will work. I've had one on Merrymeeting for over 30 years. The sailing is fun but it can be frustrating. With the many peaks, ridges, and valleys around the lake, the wind can be very unpredictable and shifty.
Wolfeboro Bay would be a great spot, if you can get out during the week or early/late in the season. Brewster Academy does their sailing there. But I don't think it would be much fun on seasonal weekends given the boat traffic coming into and out of the town docks.
I would expect that the sailing would be good on Lake Wentworth too.
Just be sure to inspect your boat and trailer each time to insure you aren't carrying milfoil. On that thought, perhaps volunteer to be a Lake Host on occasion? It would be a great way to meet the other boaters in the area.
http://www.nhlakes.org/lake-host-program.htm
>>I want to get involved in back stage theatre-suggestions?
There is a theater in Wolfeboro
http://www.village-players.com/
I found the link via the town website community links
http://www.wolfeboronh.us/Pages/Wolf..._WebDocs/links
I haven't been to the theater (one of these days!) so can't comment personally.
>>I produce professional video and compose my own music on the side-ideas for what I could do in the area?
There is a thriving music community in Wolfeboro. The Great Waters folks, the music series held at Brewster, ... I won't repost the links. They can be found via the town site or Chamber of Commerce site above.
>>I paint landscapes with water colors and want to get better at it-classes, artists?
There is a artists show in Cate Park each July. Perhaps start with contacts there?
>>I am looking to sail on bigger boats on the lake and looking for owners who may want an extra hand on their crew. Where should I go to hang out and find other sailors?
The NH Boat Museum opens this weekend. I know many active Winni boaters, both sail and power, are members there. I would guess it would be a good place to make contacts.
>>I love listening to live music, jazz especially-any venues?
See above concerning Great Waters concert series and Brewster. Not so much jazz, but a start.
>>What spectator sports are around, festivals, general fun crowd gathering type events?
Well we have a group that plays a softball game every 4th of July at The Nick
The 4th of July Parade is a great Wolfeboro tradition. First Night on New Years. Weekly concerts at the bandstand in...Cate Park! (highly recommended). Huggins Hospital Fair... You won't be bored if you don't want to be.
>>Dog and fish supplies? Dog groomer? Best vet?
My wife could better answer these as she is the primary caregiver for the dogs. There is a new pet supply store downtown, next to the Downtown Grill.
I'll let others join in to help with more. Hopefully this gives you a start. Good luck!