No worries.
You should be ok if you take it to a local independant garage with a good reputation, just don't take it to one of the big chains like ATS or kwikfit etc. Will be simple to diagnose for a mechanic.
The power measurement tool is called a multimeter and they are less than £10 for a basic one. Plenty of good videos on youtube if you want to learn to use one, it's pretty simple to do basic stuff like measure voltages etc