An FRU is also called a Field-repleacable Unit and is usually an assembly that is easily removed from an electronic equipment, laptop or just a computer and replaced so that one does not have to take the entire system for repairs. When trying to equip yourself with this unit of a laptop, you must take your Random Access Memory and your hard drive as they contain the whole information on the laptop.
0.75 miles of range is a low distance for a WAN (Wide Area Network) so a point-to-point WAN tehcnology such as IP-sec or SD-WAN can be preferred. But the least expensive option would be choosing IP-sec as specified in the question.
