I don't know what Mars/CAP is...
MARS is the Military Affiliate Radio Service. They use HF and VHF frequencies near ham band to forward personal messages to/from military personnel. Very useful during major mobilization like we are seeing now.
CAP is Civil Air Patrol. Part youth group and part domestic search and rescue auxiliary for the Air Force. They also use frequencies near ham band, and ham volunteers, to coordinate search activities and relay messsages.
The mods you referred to are only authorized for those formally affiliated with one or the other organization, and the frequencies are for official use only.
Modifying a rig for these frequencies is perfectly legal, but using them if you are not affiliated with those groups is not.
I am sorry to say that if you bought the radio with the intention of using it for anything other than amateur, MARS or CAP, you have wasted your money. Although I doubt it will happen, you might try to get your money back from the Antenna Farm. I have not bought anything from them, but from what I understand, the do not exactly have a stellar reputation when it comes to customer service from what I have read on some of these forums.