There are three components to the typical APRS environment:
- the "tracker" - transmits beacon messages
- the "digipeater" - these are optional ground stations which relay beacons to increase range and have special understanding of beacons to avoid repeating forever
- the 'iGate" - is the gateway between the radio network and the internet
There are a number of companies selling very small trackers. These are easy to install in an RV. Some people install it in the fuselage somewhere and have an external antenna that is very similar to a COMM antenna. Some chose to install it in the fiberglass wingtip with an internal antenna bonded to the inside surface of the wingtip.
Since the tracker is a transmitter operating on an amateur radio frequency, you are required to have an amateur radio (HAM) licence. In the USA, the lowest level licence is the Technician Class.
There are a number of very good "sticky" posts in this forum for getting started, equipment reviews, etc.