First Boat, Wellcraft v-20

[Destroyer]

OK...
Towboat and BoatUS: Both are good.
Yes, West Marine is in partnership with BoatUS. (That's the service I use). You can buy directly from BoatUS online, or from West Marine either in-store or online. Same cost either way. The basic tow service is $150. For an additional $14(?) you also get trailer coverage, meaning that if you should break down while trailering your boat they will come and get you and your boat home (up to 100 miles) free of charge.

Trim Tabs:
Trim tabs are flat pieces of metal, usually around 18" X 8", mounted on a hinge to the stern of your boat, right at or just slightly above the edge where the vertical stern and the bottom horizontal surfaces of the hull come together. Although their exact size differs from boat to boat, (depending on the size of the boat) the function is the same for both the electric and the hydraulic types. There is an actuator or a hydraulic cylinder mounted to them that either lifts or forces down the tab. They act on the hull of the boat much like the elevators on the rear tail of an airplane do. Their primary function is to control the pitch (and to a limited extent the list) of the hull as it moves through the water. You can get a better idea of what they look like and how they work by clicking on this link: http://www.bennetttrimtabs.com/guidetotrimtabs.php

Hope this helps clear up your questions.