right, I have limited understanding on this but here goes...
Pin 4 is a divider pin. you connect to either ground, open or V+. this will give you added depth allowing for a deeper pitch range. The divider may not need to be used at all, but I like to keep my options open and run it both open and to ground.
Pin 1 goes to V+ and to the right lug of your pot.
pin 3 goes to the middle lug.
use a trim pot in line with the pot as you would when replacing any timing component.
Also try feeding the output into the original timer, I didn't try this with my SK, but it worked well on the coiled vtech stuff
You'll have to use a multimeter to find a 5V connection to hook this up to otherwise you'll fry it with the 7.5v the casio uses. I built a voltage regulator for mine, but that was pretty pointless as you can find a 5v in a few minutes of probing.
It's good to have an alternate power switch for this n' your sk as it will consume battery power even if your sk is off.
Also hook up the original timing componant so you can switch between the two. I found it crashed mine out occasionally, especially when batteries are running a bit low. but it's nice to be able to return to the original pitch.
Are you planning on making the board from scratch?
I'd seriously consider just buying them premade from getlofi. I really wouldn't fancy soldering to something that's smaller than a gnats cock.
There's some useful info about the ltc1799 on both Getlofi and on Sailormouth if you haven't already checked it out.
hope I've helped.
Luke