Either buy unlocked or try unlocking with guidance of someone who knows. I was once in your position few weeks back. Worried and all if I screw up the phone.

Then after intensive reading around, I discovered WinPWN tool - like someone said above, one of the most effective way of unlocking without hassle

I used WinPWN and PWN the phone, and I only seem to need to use the bootneuter to neuter the modem only once.

After that if i restored from iTunes (using the PWNed firmware) it's already good Don't need to bootneuter again.