The job is nasty and I fully agree that it makes no sense to not replace the evaporator at the same time but make sure you buy a genuine MB evaporator because the connection at the bulkhead is a real pain . The copy parts tend to be inaccurate in this area and can make reconnection impossible! If you do attempt the job yourself I would advise taking photos or notes on the many connections and vacumn pipe junctions, be very carefull unhooking the wooden centre console section and leave the steering lock well alone. I think the 4 to 5 hours is a bit optomistic I would say a carefull 1 day stripdown and another good day to rebuild. If you do entrust the job to a garage make sure someone does it with 129 experience unfortunately these cars are now classed as old by the dealerships and often given to young trainees with no experience what so ever! I hope all goes well for you just remember to label or note everything because its so much harder trying to remember later. I see you are unfortunate enough to own a P38 Rangerover this model is plauged with heater and electical problems! Regards Linds