I can identify completely. I'm 46 and was thrilled to get my Wizard of Oz 4 months ago. Like you, I didn't know a lot about electronics, but was willing to learn. I think I've put almost 600 games on it already and in that time:

1) The crystal ball showed a blank or weird message screen.
2) The castle flipper EOS switch was stuck .
3) The Munchkinland playfield was beginning to get beaten up by the ball smacking it too much above the rainbow targets.
4) The main left flipper would not settle back to its normal resting position, and would creep up higher and higher each time I used it.
5) It was running an older version of the code.
6) The flying monkey man wasn't picking up the ball.
7) The crystal ball VUK would take many repeated tries to kick the ball back to the playfield.
The drop down target blocking access to the castle upper playfield was set too high and the ball would occasionally get stuck above it.

I've remedied 6 of these problems by reading the manual and watching videos / reading on the pinside forums. This has given me the confidence to dig in to it more. You will get there in time, so don't give up. Great resources can be found with fellow pinsiders. I recommend reading anything by vid1900 and LTG .
I'd focus on the things that make the game playable. The code is pretty good with Wizard of Oz and the game has a lot of ways to play around bad switches. Best of luck!