scangauge II

i have a scangauge II. a have emailed the company several times and never got a reply. i have a few questions and wondering if anyone can answer me.
if it matters the vehicle i have is a 99 montana/transport
1 - the instructions says it can be moved from vehicle to vehicle, so how do you do this without screwing up your trip memory as it would just to read from the new vehicle and when you put it back in the original vehicle the trip would think you have driven when you really have not (i hope this is understandable).
2 - is there a way to get oil pressure readings, oil temp, trans temp ?
3 - sometimes when i have been driving for a while (like on the highway) and i let off the gas, the readings for fuel econ goes to 0000, why ? (normally it goes to 9999)
4 - do i have to fill the tank every time ? if no how do i do it if i dont fill it ?

thanks