Welcome dear,
It is easy to swap GRFU by MRFU without the need for tools. Plz follow b/m steps
1-You should have a laptop & USB-ethernet cable & LMT SW
2-login UMPT card and in MML window run command "RMV BRD "
3-after removing the board from UMPT plz turn its power off and remove it from its slot inside the cabinet
4-now install a new board MRFU in the same slot and turn its power on
5-in MML window plz run command "ADD BRD" and choose board type MRFU
hope that help you my friend