Actually there was nothing wrong with the aeris kit, it was from 2014, well maintained, everything worked great, kinda wish I didn't trade it in now to the shop, but was told it was a safety issue since the service kits aren't available.No and no.
I also suspect that you could get your aeris regulator working fine again, but I couldn't be sure about it. Based on your comments, I would venture a guess that this dive shop was much more interested in selling you a regulator than fixing yours. What you are buying is a much higher end regulator, in either case. Don't worry in the slightest about the MK17 being an older model. It's still much newer and fancier than anything I use for cave diving, and I'm still alive, and still cheap!
Seriously, the hype around regulator sales is kind of nutty. I guess dive shop owners have to make a living too.
I'm a cyclist and the gear discussion is really similar to shinano dura-ace vs ultegra vs 105. Marginal gains for big price differences and endless perseverating over "did I make the right decision?"when they all functionally do the same thing and just cause one's brain to hurt and a million open chrome tabs with reviews. Hell, I think the HOG kits seem like a pretty good deal after doing some reading here.
I talked to another shop tech at a different store that said the d420 wasn't selling as well as SP hoped and was concerned about replacement parts in a few years. I left a message for the dive shop about switching for the mk17/g260, it's within the return period and unused, hopefully they don't get too angry