I just went through the same evolution - VM1000 to a MFD GDU450, adding to my existing GDU460 PFD. Yes, the fuel, manifold, and oil pressure senders are not re-usable - GEA24 prefers 2 wire 0-5V senders. But, the FloScan fuel flow should be re-usable, as the GEA24 allows K factor input by you (But, good luck determining the K factor of your current sender). That said, I would highly recommend while you are at it to replace the FloScan, as the Garmin spec'd red cube sensor has an accurate factory specified K factor and most folks report it as being dead-on, i.e. reported fuel usage matches fill-up experience perfectly. Also, note the VM1000 CHT sensors are type J, not K. But here too, I would recommend splurging on new, especially as the EGT probes do deteriorate.
Have fun with all the new wiring!