It can often be difficult to find answers to these queastions in standard aviation texts. Don't be afraid to do a google search for these terms if the FAR/AIM is driving you crazy.
Flight Watch is focused on weather, both reporting and pireps. As mentioned it is available on 122.0 pretty much everywhere as long as you are above 5000 ft., often lower. Call them by asking for XXX Flight Watch, for example Los Angeles Flight Watch.
Flight Service offers the full range of services including weather, flight plans, NOTAMS, route briefings, etc. They are often available on 122.2, but this varies by location. See your sectional for local frequencies. Call FSS by asking for XXX Radio. In addition it is helpful to say the frequency you are using and your approximate location. This is because each FSS typically covers a large area with many remote stations. Here's an example of a call-up. Rancho Radio this is Cub 114DE on 122.2 near Bakersfield.
FADEC and auto-throttles are different things. FADEC integrates throttle, prop and mixture (in a piston engine) into a single power lever. Continental has done a lot of work in this are, and Lycoming now has a FADEC engine in their new TEO-540 engine, which is so far slated for UAVs and the experimental Lancair Evolution. Jets also have FADEC.
With FADEC you only have to move one power lever to control the engine, but you do have to move it yourself. With auto-throttles the power lever is connected to the airplane's autopilot, so the A/P can adjust the throttle setting as it sees fit to fly the airplane. Cirrus is working on an auto-throttle setup for its planes, but that is for somewhere down the road. Right now auto-throttles are only found in airliners and high-buck biz jets.
