Priiloader 0.4

I have Wii 4.2 E

I installed on my Wii PimpMyWii 1.42 and BootMii as cois and get backup NAND.bin and key.bin

Now i wanna get priiloader 0.4 for protect my WII against brick.

But on Wiki Priiloader i saw next caution

IT IS _HIGHLY_ RECOMMENDED TO INSTALL PRELOADER ONLY ON A WII WITH UNMODIFIED IOSs!!

What do they mean ?
Could i install priiloader after all changes that i did ?

Yes, it sounds like it is fine.

The Wiki is referring to the IOS that Priiloader runs on, usually the system menu IOS. In your case, this would be IOS 70. As long as you haven't done anything to IOS 70 (not sure why you would want to) you will be fine.