unblocked s3mini update to 4.2.2 or higher?

[AC Question]

Hi I have a Portuguese samsung galaxy slll ming - gt-l8190 working n android 4.1.2 and want to know how to update it to a higher versin of android. Either to 4.2.2 or even kit kat if the phone will allow it. I do know some about phones but maybe not as savvy as I wuld like to be, so an idiots guide would be great. Also are there any negatives in updating as I dont want to stop my phone from working!!!!