Download a manual from buellmods.com It has basically step by step procedures to check everything you need to check in the electrical section. It has flowcharts to walk you through it and procedures that basically tell you how to do it. If you cant follow the flowcharts and the manual you are in over your head but the forum might be able to help with specific questions after you start your way into it.
https://www.amazon.com/Innova-3320-A.../dp/B000EVYGZA
Something like that would be plenty for your needs. Auto ranging is a nice feature to have.