It’s really difficult to find instructors who know this stuff – even today, a decade after these boxes started to appear.
When I got my TB20 in 2002 I could not find an instructor who knew how the HSI (a 1982 instrument, in this case) worked, and learning how to fly a GPS approach with the KLN94 was totally out of the question (especially as there weren’t any GPS approaches in Europe, probably).
There are a few freelancers who specialise in advanced training but they charge quite a lot of money, they often don’t travel to you, and you find out about them only by joining type specific forums so you have to actively seek out advanced training which is against human nature 
In the UK, you could count them on your fingers. Obviously, most “G1000-type” pilots will never get anywhere near one. They use the box as a very simple GPS navigator.
follow STARSs flying DCT RNAV fixes on arrival
I’ve never heard of anybody doing that, nooooo, not ever 
But really airports have themselves to blame for publishing arcane “RNAV” or “PRNAV” procedures which are almost never flown except maybe for the very first segment. Nowadays there are airports that publish maybe 30 PRNAV SIDs/STARs and you can bet nobody flies them because the whole lot is radar vectored. Even “old pilots” will need their brain reprogrammed if these procedures (the drafting of which created a lot of nice jobs somewhere) actually start being used as published. Also most planes+crews are not PRNAV certified so it’s a case of “don’t ask the question so no lies need be told”. Somebody told me that if the procedures published for the London airports were to be actually used, instead of radar vectoring, the system capacity would fall to 20% of present.
