Yeah I love the printer itself but can't stand HP support. Their support is really bad...I have a few horror stories about them but I'll spare most of it in this conversation. Moral of the story is their techs are not as savvy as they should be considering the amount of money we pay for these things and their support.
I like to think I'm pretty good with them...been using the Scitex line for about 10 years or so. And ran a Colorspan before that which is a similar machine. I've changed/diagnosed all the most common issues, headboard, mother board, I/O board, heads, filters, manifold, data cable, ink lines, encoder strip, encoder reader, drive pulleys,....pretty much all of it except the drive motors and media belt. But the drive motors would be an easy fix/diagnostic, just haven't had that issue come up. I find diagnosing is perhaps harder than actually mechanically changing the part, as long as you take a good shot of bourbon before doing the work (keeps the shakes away, lol kidding, kidding). And I'm a believer in helping people with whatever talents I've been gifted so if you need something I'm happy to help. I'm by no means an official tech or anything but I have learned a lot keeping my own equipment in order.
I'm decent but a real guru is Mike at California Media Services. He's been my mentor on the Scitex line a few times and I can't speak highly enough about him. Last I spoke with him was a couple years ago and at the time he was the only one in the country still running the FB950, he had a whole bunch of them and I was buying parts from him instead of HP because HP dropped support on their own machine.
Just a side note....I've had some pretty terrible experiences with HP support. And on the worst of them I talked my way up the food chain until I got to an executive which in one case they screwed up so bad that they didn't charge me at all. It's a long story but we are talking about a $25,000+ mistake they made and I fought very hard but eventually the executive agreed to not charge for the whole thing. It was a big mess and I appreciated them owning up to their mistake, but had I not fought tooth and nail they would have charged me for it. Even though it should have been a $5000 routine maintenance that went haywire! So I'm not sure of your situation but be very firm with them and don't pay anything that you shouldn't have to, because they will charge you for it if you don't!