The good thing about mistakes in this hobby is they can always become something else - I have a custom designed cocktail cab that is now my router table ....or buried in the backyard
Friends and family only need see the good / better / best projects ...but we should see them all
Personally I think designing the cab is the hardest part - because its often dictated by how good your skills are (or perceive to be) to then build it ...and how much you're willing to challenge / push those skills.
When you get to the wiring / making it "actually work" stage - that part is easy (yes it is Jennifer!), we can talk you through it / point you at some good videos, JAMMA isn't hard to understand - if you go the MAME route you will need some reasonable PC skills, I recommend sticking with JAMMA as a good starting point
Main points are:
* Define what you want and how it should look
* Workout how you plan to build it - break that down into stages
* Ask for advise (or recommendations) on how to proceed through each stage
* keep moving forward.
* Enjoy yourself - take nothing on this forum as personal
* Embrace time, don't fight it
All the best!