Do not know, nor had any experience with coilovers at all, so bare with me guys:

Once you installed your coilovers...and decide to adjust the height, what is the process:

1.) Do we...take the wheel(s) off and then adjust, or you can adjust with the wheel(s) on?

2.) Does it require jacking up the car? (ie. in a shop, 2 wheels up, or can do it with one wheel up at a time)

3.) Do we have to get another alignment done once you put back your stock wheels? (Let's say i have 19's on and putting back my 17's)

I apologize for the rookie questions...i wanna do it right come spring time --> i have my eyes set on megans...but came across some tein basic coilovers too for the same price ($900)...only difference is megans have 32 damper settings (?) if someone could shed light on this, that'd be awesome guys!

 

Yes, the wheel need to come off. You can do one at a time.
If you change the ride height, that changes the suspension geometry and the set angles move from their position. This means you need to get an alignment to correct the settings, when you adjust the height.
Changing your wheels does not require an alignment.

Damper adjustment allows to change how firm or soft the shock dampens the spring. For example, if you like a softer ride for the street, and firmer ride for autocross or road racing, this comes in handy.

There is a ton of info on coilover kits here for the 3G.

 

Yeap pretty much what powerflow said hitt it on nail. But to answer your questions you can adjust the coilovers with the wheels on or with the wheels off some people prefer to do one or the other.

Yes you will have to jack the car up, in order to access the coilovers to adjust them.