Good to hear that he likes it!!
Tuning is a little more time consuming that with a non string locking guitar; here's how I go about it..
... 1. Take note of where the bridge plate is sitting in relation to surface of the body of the guitar - I have mine sitting about 2mm lower at the back edge than the front.
2. Remove the old strings by unwinding them, after undoing the locking plates on the stringlock - never just cut them with sidecutters or the like! If you have a whaletail on the trem, then you may need to put something on the surface to protect it from potential damage - a bit of cardboard etc.
3. Clean and tidy up the areas you normally can't get to easily, and oil the fretboard.
4. Put all of the new strings on, noting that they go on the same way the old ones come off!
5. Quietly bring all of the strings up to pitch, give or take. and then stretch them by pulling one at a time upwards quite firmly, then re-tune. At this stage you realise that you've not set the fine tuners in their optimum position for re-stringing and you do so -
- by setting them so that 90% of their travel is to sharpen flat strings. Stretch and re-tune until you have a stable state of tune then check and reset the intonation if it needs it.
6. When you're happy that you've got a stable tune, then put the the locking plates on the stringlock and nip them up - DO NOT OVERTIGHTEN. Re check the tuning and adjust if necessary on the fine tuners.
7. You may find that it wobbles away too much for your liking, in which case you're going to have to shag about with the spring tension in the back, by adding springs or winding the spring claw in a bit, all of which requires re-adjustment at the top of the guitar.
Pickup height in relation to the strings is a tricky one - there is a formula somewhere that I've seen, but by and large, the closer to the strings, the higher the guitar output. BUT. Too close to the strings and there'll be electromagnetic damping of the strings by the pickup magnets which is undesirable because the strings can't vibrate freely. Fiddle about with the height adjusting screws on the pickups and let your ears do the selection!!