I'm not down playing my mechanic but if I got these, I was thinking about getting them installed at an actual suspension shop.
If you are looking for suspensions shops to setup coil-overs then here are some things to ask or listen for:
1) Can they do a full alignment or do they have a shop they will get it done at
2) Can they do a 4-corner balance or at least know what it is
3) Can they check and set the ride height (not wheel-fender gap!)
If the answer isn't yes to all of the above then move on. Suspension is a tricky beast if it's done wrong and I'd like to have confidence in the place.
For the record you don't need a 4-corner balance but a reputable suspension shop SHOULD be able to do it. Basically what they are trying to do is balance the weight on all 4 tires, with you sitting in the passenger seat, so that the tires are equally balanced. You should not have to explain this to them. It should be a more or less yes or no answer.
Ride Height is also checked by measuring the distance from the point where the sprung and un-sprung weight meet to the ground. This is typically the outermost bolt on the lower control arms. You can also cheat and use some other reference point like frame rails, etc. I don't care for using fender lips as they can be off compared to the actual chassis frame.
The place I found near me quoted be $750 to do the full setup. This included installation, setting ride-height, alignment, and 4-corner balance. I could also install them myself and then just have them do the rest. About half the cost was installation and setting ride-height.
If you want to install them yourself you can get somewhat close by just measuring the over all length of the shocks and setting them the same. You also want to set the spring pre-load to the same on all shocks to start. To set the spring pre-load you would back the lock nut off till the spring is free, then tighten it down so it is just barely snug. You can add pre-load, which is the force applied to the spring outside of the cars weight, by turning the collar and tightening the spring. You will want to count the turns you put on each shock as they should be the same from left to right. You will want to start with 0 pre-load which means the locking collar is just tight enough to hold the spring in place without it being loose or wobbling. You will want to set the pre-load on the spring so that about 1/3 of the shocks travel (about 1.25") is pushed in when the car is sitting idle on a level surface. You do this by adding turns to the spring collar making it compress the spring. You should never remove turns from the collar as that would allow the spring to float during extreme suspension maneuvers. If you need to subtract turns then you need lighter-weight springs.
You'd start with the shocks the same length, then adjust the pre-load so that the shock is compressed 1/3 of their travel, then you would go back and adjust the lower half of the shock to set ride-height, then double check the pre-load again (or do the 4-corner balance if you have scales). After that it's off for an alignment. You should also add a slight rake from front to back. The back shocks would want to be one-turn longer (the lower half, not the spring) then the front. This is because the wind pressure going over the windshield and cabin area will push down on the car and flatten it out behind the front wheel (like a fulcrum). If the car is flat to begin with then you can end up with the back riding lower at speed then the front which creates an air pocket under the car, lifting it, and reducing down force and traction. By having the back slightly higher then the front you can increase the down force some while making sure that when the car flattens out you aren't catching and unnecessary air under it and losing traction. Your front shocks should also be set stiffer then the rears.
Here is one hell of a read if you REALLY want to know all about setting up a car:
http://www.racelinecentral.com/RacingSetupGuide.html
Granted they are talking about nascar chassis and rules, but its all the same working theory.
