It is very easy. Nothing at all to taking it off and putting it together again just means setting engine to tdc, lining the dots up on the pump&drive and slotting it in (with a bit of a twist as you go). You know when you've got it right because the distributor tang is in the right place.
In terms of checks while it's off, you can easily remove the pressure relief valve cover and check
The plunger moves and all is clean, but if you want to do more and take it apart you'll need another gasket and the fsm instructions for checking clearances - which is also easy but not sure if Haynes covers it
Ditto, what Jonbills has said. If you are careful removing the pump without allowing the drive shaft to drop out, it should be easy to put back in the right place. A tip is to put a bung into the hole to stop it dropping. Get the engine to TDC on no. 1 cylinder first and make sure it doesn't move.
If you do take it apart and feel inclined to check the tolerance measurements for the rotors they are:
Rotor End Clearance - 0.0024" (0.06mm)
Cover to body clearance - 0.0016-0.0032 (0.04-0.08mm)
Rotor-Tip Clearance - 0.0047 (0.12mm)
Outer rotor to body clearance - 0.0059-0.0083 (0.15-0.21mm)
The are taken from the 'How to rebuild your Nissan & Datsun OHC Engine' book.
Check for grooves or scoring on the outer rotor and casing by scraping your nail across the area and if you can feel a ridge, chuck it and buy another one. You could try to remove them with fine emery cloth but you risk increasing the tolerances and making an oval so I would avoid if possible.
When you put it back together if it is ok, you should see 2 arrows on the rotors these must line up and they should not be visible when you put them back into the body.
Good luck.