A mechanical mod is a battery tube with no wire, solder, or circuitry. They consist of three main parts: A battery tube, a switch, and a an insulated positive connector. The whole mod with exception to the post that touches your atomizer is the negative part of the circuit. With an atty on your mod, you push the switch, and it closes the connection in the body of the mod, allowing electrical current to flow from the positive side of your battery, into your atty, through the coil, out your atty's threads, into the body of the mod, through the switch, and into the negative side of your battery, ad infinitum (well, until your battery runs out, blows up, or you stop holding the damned switch down, you vapin' maniac you).
You do not have to use an RDA/RBA. Any commercially available low resistance (usually about 1.8Ω) should give a decent vape, unless you like cooler vape, then feel free to play with standard res (2-3Ω).
As for a decent setup, you can spend any where from the $20 range for a cheap Chinese knock-off, that still performs well(some of these take tinkering, others are good out of the box, to 40-$50 for the recent Smoktech mechs (Magneto, Galileo, and Smooth), all the way up to 150-$350 for a high-end mod.
On top of that, you'll need some batteries, the AW IMR's are the most highly recommended:
Genuine AW Batteries at RTD Vapor
And a charger. Nitecore i2/i4, and Xstar chargers are good directions to look.
As for other links, you might clarify what you still want to know, There are tons of great articles. I researched every day for a month before I ever got my hands on a mech.