Was Arnie actually good at fixing cars?

He did take auto shop.


Norman- Apparently, The Whore is calling.
Norman- You were just using me. You son of a bitch!

he did some of the building but in the book the car does most of it like the windows

Look how cockeyed he works... brand new windshield wipers for a busted windshield. 

He did the original restoration job himself. Christine only repaired herself after she was trashed by Buddy and his gang. Darnell mentions to his Dad (I think) that Artie has good hands but he thinks he'd be wasting his time.

Arnie just did lubes and oil/filter changes. I mean, c'mon, cars need people to fix some things. They can't do it all by themselves.

You can't polish a turd.

Don't put the devil in the picture, cause' the religious groups won't wanna see it.