hi its a d1 i have as well good heater, these can be repaired at home with no computers unlike the newer one,i have found they go thru heater plugs if used a lot, they are ?50 from eberspacher but you can buy other makes for about ?20 on ebay, there is loads of info on them on the boating forums as well.
things to watch for are poor electrical connections on the control box and poor voltage, i find its best to start the heater when the engine is running, bore and length of fuel pipe is critical as thats what meters the fuel, exhaust and air inlet should be matched lengths as well and theres a minimum length to them around 500mm i think,
the glow plug relay is the same as your landrovers one (smaller of the two boxes)
i have mine just blowing into the cab it gets so hot that ducting the heater isnt really neccesary and beware the ducting gets very hot,
i have the parts/manual cds if you need any info from them just let me know