You you have a mod chip that can be turned off, then yes. If you can not turn off your mod chip, you wont be able too.
Yup, if you disable your chip before going online, then you'll be fine. If you have a ver 1.6 however, you will need to add a switch to turn the 5v power off from the chip, because on a ver 1.6 the 5v is always on....