All below my personal opinion...
assuming you mean an online one, there are lots of (free) youtube presentations of varying depth and usefullness but if you want a reasonably thorough and well thought out course on the G1000, King Schools offer one for $199 USD.
https://kingschools.com/flying-the-g...-online-course
They can be, at times, cringy presenters but actually do a good job IMO and cover it quite thoroughly. It is about 7 hours of material. I used it some years ago to rapidly get a handle on the G1000 and thought it well worth the money at the time.
If you baulk at the cost think about how much it would cost to hire an instructor to sit down with you for a few hours and go through it with you, plus you can go back to it and refresh yourself any time (once you pay for it you own it).