"What is the difference between 40,60,70,80,92,&120mm Fans?"
The bigger fans are quieter while pushing the same amount of air. Smaller fans are needed for tight places like on your high-powered vga card. Generally speaking, replacing small fans with big fans is a way to quiet the system down. imo all cases should have one 120mm quiet intake fan and one 120mm exhaust fan, standard.
"When I buy the CPU is the heatsink that comes with it honestly good enough?"
I've tried several on my systems and the actual heatsink is a smaller overclocking factor than the fan's cfm that is on top of the sink (cfm stands for cubic feet per minute of air pushed), a smaller factor than the temperature in the room, a smaller factor than the motherboard, a smaller factor than the congestion in the case, and a much smaller factor than the specific cpu core type, manufacture date, and serial number which gives clue to its oc ability. For stock speeds, the stock hsf (heatsink/fan) is always good enough. For overclocking, you will need a loud fan to have much of an impact on your max overclock speed. An sk-7 with a thermaltake II fan is good for oc'ing because the fan can be cranked up to a high cfm and make a definite diffference in your oc, but is quiet at lower cfms.
The presence of so many variables makes it impossible to compare temps between people, and makes it easy for buyers of hyped-up aftermarket hsf's to believe they have substantially improved their system. Go ask the guy who just replaced his factory-supplied tires with some nice aftermarket tires and he'll tell you about his better gas mileage and faster time from 0 to 60. Tires, like hsf's, only really pay off in extreme confitions. A good rule of thumb is that if it ain't a lot louder, it ain't much cooler. All that said, hsf's are fun so I blew $20 on an sk-7, which lowered my temp 1C over the stock amd hsf. (Although its a cold morning right now so I get to tell myself it got me 7C)
"Do the chipsets have fans too?"
Sometimes. The northbridge is fan cooled on some boards and just has a passive heatsink on other boards. Its always a small fan that is louder than its worth when a board has one.
"What exactly do controller cards do? Is that what RAID is?"
RAID isn't worth it. Raid allows data to be spread across mutiple drives to enhance reliability. Corporations use it, home pc owners don't need it.
"Is there any other general knowledge I should have?"
If you can get your hands on a free pc, no matter how old, taking it entirely apart and putting it back together is a good experience.
There's a million software tweaks and freeware utilities to be had and learned about aside from hardware. Motherboard Monitor, cachemaster, sisoft sandra, tweakui, freeram xp, 3dmark, are a few I use.
When you setup your system, I recommend you partition your hard drive into two drives so that if you ever need to reinstall windows on c: you can keep d: intact.