best money you will spend for a long time, don't skimp on the head unit either.
I bought the SIno brand here in the UK
at the time I blogged the following observations
1/ the scales come with small yellow plastic tabs holding the reader head to the scale itself, at the correct "ride" distance and so forth, leave these in place until the last minute, they make setup a lot easier.
2/ for each scale note they only fit the carriers properly one way around, but the head unit has the facility to select the direction of reading for each scale so don't worry about getting them the right way around.
3/ mounting the scale is straightforwards enough, just make absolutely sure that you install it perfectly parallel to the direction of motion, do NOT try to mount the reader head before you have the scale set up perfectly parallel.
4/ once the scales are fitted, you can move on to the reader head mounting, before you attach the reader head to the mounting, do a couple of full travel tests, make sure travel is inside scale limits, and make sure head / scale separation remains constant throughout travel, ONLY THEN can you attach the head to the mounting.
5/ If, like me, you bought the slimline scales, you're in for a lot of fun if you take the dimensions shown in the supplied literature as being gospel, so, think thrice, measure twice, cut/drill/mill once.
6/ The only things not supplied in the kit that you'll need apart from basic tools are a set of 3, 4 and 5 mm taps, numbers 1, 2 and 3 to each set, and appropriate twist drills, and a decent vernier, scriber, set square and my preference of using a battery drill to run the taps in and out.
7/ Now you're at the stage I'm at, and only things left to do is tidy everything up, clamp back the armoured cables, etc etc.
8/ It took me an easy going relaxed day to do the X and Y, and to get as far as I could with the Z in preparation for buying some 8mm silver steel rod this am to make the Z linear slide so that I could fit the Z without worrying about the reader head / scale clearance changing during quill travel.