Some lights about not-oficial android upgrade topic

I dont know if there is a specific part of the forum for this problem, so I posted it here.

Well, I recently bought a Samsung Galaxy Trend (GT S7560) that came with Android 4.0.

I've been reading around that you can upgrade a device with a newer Android, even if it is not oficial.

I'd like to know how can update my phone to Android 4.1 or 4.2, if this would be faster (less lag) and this process will void the warranty.

Thanks in advance