Personally, I didn't find the abc's of reloading all that helpful. Lee has some neat reloading video's on there website, and the Nosler manual has some nice step by step instuctions in the beginign of the book. Also, not to direct traffice to another site, but "The Firing Line" reloading forum is quite busy and has alot of good info with a pretty good starter thread....
For the New Reloader: Equipment Basics -- READ THIS FIRST - TheFiringLine Forums
Cartridges need to be trimmed every so often as the neck stretches just a hair every time you fire a load.
Case trimmers are pretty easy, I have the basic Lee ones and they work great. Basically a case trimmer has a base that locks the shell in place and a guide with a cutting head. Lock the shell in, insert the guide and turn the cutting head. The cutting head will shave little bits of brass off until the guide bottoms out then it will cut no more.