You may want to read a thread I started a week ago about UV dye to detect leaks:
Where can I get fluorescent dye for a/c system?
There's mention that a kit is available at WalMart that includes dye and a light. If you can't get it there, you're sure to get it at acsource.com and ackits.com.
For tools, you'll need manifold gauges and a vacuum pump. Try eBay for gauges, a lot of mechanics are selling off their r12 manifold gauge set. After that it's all plumbing and hooking up the lines for evacuation and recharge. Ideally, you'd want to charge into the vacuum, that is, with valving as opposed to connecting and deconnecting lines.
You may want to lean on the guys at aircondition.com. There's a wealth of information there devoted entirely to automotive air conditioning.
If you only need to top off only once a year, you may not need any repair. I'm not sure where the line is drawn between normal leak and fast leak.
On a final note, have you considered charging with HC (hydrocarbon) refrigerants? It's worth considering if you plan on doing all your own a/c repair on your vehicles. It's a touchy subject though... VERY popular in Australia but looked down upon by many in the US.