The only HD DVR that would require the DTV SWM technology is the Genie (HR34/44). If he has one of those it will work with that LNB but you are going to add some special hardware between the LNB and the receiver. This is a SWM8 switch and a power inserter (different than the PI in his home).
It's also unlikely that you are going to be able to change your current LNB to the SWM3 LNB listed above if this is a tripod mounted antenna and you absolutely cannot change the LNB if it's an older roof mounted manual satellite dish.
Find the model number of the receiver he is trying to use and post an update.