Hi, Noah.
I've replaced and recalibrated a couple of stock screens with split screens. Not a big deal, you just need to be careful you don't touch or scratch the screen. I'd wear latex surgical-type gloves while handling the screen, just in case you brush against the surface of the screen.
Assuming you replace the screen with the original Pentax replacement, you shouldn't have to recalibrate. If you go for an aftermarket split screen, you may need to order a set of shims from Pentax (around $6) and recalibrate the focus. Not difficult but can be time-consuming, as you need to remove the screen, re-shim, install the screen, take a test shot, remove the screen, try another shim, reinstall the screen, take another test shot, etc., 'til you get it right.
The good news is checking the focus is a snap with a split screen. Just lay a ruler on the table and take a shot of it at a 45 degree angle with the fastest lens you have, manually focused, and wide open. (I used a 50mm 1.4) The narrow depth of field will let you zero in on the correct calibration for your screen. Focus on the 6-inch mark with the camera fairly close to the ruler. (A foot or thereabouts.) Ideally, it should be in the sharpest focus in the finished test shot, with points to the front & rear gradually fading to out of focus.
If you use manual focus lenses a lot, I highly recommend going for a split screen. It makes accurate and quick focusing MUCH easier.
Good luck!
Bobbo :-)
Last edited by GibbyTheMole; 07-16-2011 at 05:55 AM.