Default [Q] How to do a backup of Stock Rom & Kernel before changing anything?

Hi

Iv'e searched around but wasn't my exact question.

Is there a way to backup my stock Rom & Kernel without having to modify/void my phones warranty?

I don't want to trip the flash counter either before backing up.

I guess what I really wanted to know is if there was a way to put the phone back to normal if I wanted to return for warranty like it was fresh out of the box.

I have no problem downloading the stock rom from Sammobile website and flashing that, but I believe that would trip the flash counter.
Also I don't want the warranty in download mode to read "Warranty Bit: 1" I want it to still read "Warranty Bit: 0" as to not void the warranty

I hope I'm making sense here.

Thanks for any help
Phone: Samsung Galaxy S III SGH-I747M
Carrier: Telus (Canada)
Baseband: I747MVLUEMK5
Firmware: 4.3
Rom: Stock
Kernel: Stock
Launcher: TouchWiz UI