Prolly in the minority here, but a little 3klb cargo trailer will tow fine behind any full size vehicle with decent brakes with no problem.
I've never been hasseled on my 3500lb single axle enclosed sled trailer (no brakes from the factory). I mean I've gotten popped for a couple speeders over the years with the trailer (gotta get to the hill early on a powder day!) and the 5-0 never asked about the brakes.
Yes, a 4 pin to 7 pin adapter will work just fine. $20 plug and play to get the lights working.
I would not reccomend a surge brake system to anyone who is not prepared to maintain it regularly. Have had 2 boat trailers with surge brakes. Garaged, protected, maintained and they still require work. Either the shock goes bad, or the actuator, or the brake fluid gets rusty from sitting. If you got surge brakes, plan on sucking out the brake juice at least once a year out of the reservior to keep it relatively fresh and keep a cover over the reservior cap. They will weep in moisture. Not sure why, but surge brakes just seem to be finicky.
Besides, they are easier to burn up the brakes if you dont know how to drive with them. Downhill braking frequently requires steepin on hte go pedal to extend the actuator and keep from continually applying a little brake pressure while going downhill.
Surge brakes also dont have the capability for a manual over ride to pull a swaying trailer back in line.
IMO, surge brakes will jsut turn into NO brakes in a couple years on a "community" trailer.