I would add to spend time learning the menu system. Get to the point where you can confidently go in and change things. If you make changes one at a time it is easy to put them back. Try programing the two left side programmable function (PF) buttons is a good practice exercise. It's all in the manual.
Whenever you want to make changes to a channel you first tune to that channel then press menu to enter the menu system then up/down buttons to find what you want to change then menu again to select, when done hit exit. The codes and frequencies are listed in the manual.
Also GMRS is channelized. A channel is a specific frequency. There are two modes, channel mode and frequency mode. When in GMRS channel mode you wish to see what the frequency is push the mode button on the right side of the key pad. That will switch between the two modes. When you begin to program the radio you need to be in channel mode to program for GMRS and Frequency mode for everything else such as police, fire EMS etc for scanning. In your example when on channel RPT-19 push the mode button and you will see 462.650(00).