I work for an avionics company here in Central Florida. One of the largest in the country.
You won't be able to go with a G1000 system. They are really going to be found in new aircraft as they are built onto the Type Certificate of the aircraft. The aircraft where you can upgrade to a G1000 system are going to be the Beech King Air 200 and 300 series aircraft. Upgrade like that would be in the range of $250k and above.
The best option is going to be a G500 TXi EFIS system from Garmin. Great capability with this system and our shop has done quite a large number of upgrades. We are currently finishing a Piper 6X and rolling into a Partenavia P68 Observer and Twin Commander 500. You can add Synthetic Vision, engine monitoring and pair with GTN 650/750Xi GPS/Nav/Coms. Display of ADS-B traffic and weather is available as well.
Typical full panel installation is going to set you back $85k and above.
This recent Cessna 414 Upgrade was in the $165k ballpark.
Garmin G500 TXi EFIS
Garmin GTN750 GPS/Nav/Com (Dual)
Garmin GMA 35c Audio Panel
Garmin GTX 345 Remote Transponder
Garmin GTS 800 Active Traffic System
Garmin GFC 600 Autopilot
JP Instruments EDM-960 Engine Monitor
New pilot, center and co-pilot panels
If you ever get something and are interested in an upgrade, let me know.