How to unroot Droid Razr I bought from a friend without knowing how it was rooted?

[ComplexNemesis]

I just bought a Droid Razr off ebay and when it arrived it was already rooted. I realized it once trying to update to most recent software and it kept failing. After looking around I found out that Superuser was installed. I planned on rooting the phone myself after I did the update. Should I be worried that whoever I bought the phone left tracking software? Basically I want to try and figure out either how to unroot the phone or make it able to update? Cause right now the OTA update keeps failing

[syndicate0017]

This is what you need right here.

[NEW] Fastboot Files/Gingerbread 2.3.5 CDMA Droid Razr XT912 Verizon.

[seeker613]

OK, I'm still using my Droid 2, but I've been drooling about the Razr for a while, but alas, I've had to wait until Verizon allows me to Updgrade...

so I don't know much about the Razr & the diff versions that exist; so what is the XT912 Verizon version? Also, pls confirm, the fastboot method does not destroy / wipe your files? If so, woo hoo

Thanks in advance,

Seeker