“Unless you are on PtF this should be signed off by a licensed engineer or ATPL.”
If you are on a PtF it would need it to be signed off by an LAA inspector.
An untrained person can do it right (I did), but take your time and get at least one preferably two helpers. I used a hiking compass as my landing compass, which worked ok. Some time later I fitted a magnetometer based system (in addition to the classical one). The calibration on this was more straightforward. Both are in fairly close agreement and both work ok in the air.
Rod1