Sort of. Standards Document 14 is actually a guide to Examiners, not applicants.
Look on the CAA website for Form SRG\1157. Although it's the Examiner's Record for the SPA, Skill Test and Proficiency Check, it spells out what you will have to do:
For SPA SEP Class Rating renewal, only Sections 1, 2, 4 and 5 are required:
Section 1 - Departure
Section 2 - Airwork (VFR)
Section 4 - Arrival and Landing
Section 5 - Abnormal and Emergency Procedures
Section 3A - Enroute Procedures (VFR) and Section 3B are not required for SEP Class Rating renewals or re-validations!
There is no actual need to study any radio navigation to reactivate your PPL; however, your intention to do so is very laudable and I wish more people would learn how to use the expensive avionic equipment in their aeroplanes. But I suggest that you sort out your PPL first, then go flying with an instructor at a later date to teach you properly. We have our GPS equipment set up to indicate present position; however, we do not teach pre-PPL pilots how to 'navigate' using GPS. Position fixing using VOR, VOR/DME, ADF is taught to PPL students as is tracking a radial. But that's the limit at PPL level.
Perhaps you should consider doing an IMC rating? That'll certainly teach you how to use the aircraft navigation aids.