So, you're talking about replacing the fuel sensor, right? Not the whole Grand Vista?
Changing out the fuel sensor on the Grand Vista 250 is actually a pretty simple job. Just take off the seat, remove the panels, disconnect the battery, unplug the old sensor, swap in the new one, and then put everything back together.
I've tackled a few of these myself, and the key is to make sure that the new sensor matches the model year of your vehicle.
Do you already have the new part ready, or are you still on the hunt for it?