The radio version you have is from RUU 1.11 which is one of the oldest ones for this device. I'm curious to know how it's still there unless you've never done an OTA/Hboot downgrade.
It will not erase your handset, only updates the radio software which is a completely separate part of your phone. Just follow the instructions and read through them a few times. I've upgraded/downgraded my radio several times following those instructions.
Nexus 5 (16GB; White)
Nexus 7 (16GB; 2nd Gen)
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