First things first, u need to make a nand backup just in case shit goes sour with the rest of the solution.
You should have a "bootmii" folder on your sd card, if you're missing it, start ModMii Classic, then enter 2,BSD,d,y to download the bootmii SD Card Files to your sd card. Then, with that folder on your sd card, turn on your Wii. If the bootmii menu starts up immediately, that's great and it means you have bootmii installed as boot2, if it doesn't start just launch bootmii either via preloader or via the HBC (press home then select launch bootmii). Once you've loaded bootmii, use the power and reset buttons on the Wii (move and select respectively) to make a nand backup (picture of chip pointing to sd card).
After you've successfully made a nand backup, u can concentrate on reinstalling your system menu IOS and system menu (which uninstalls priiloader) - in your case you can install a patched IOS60 and system menu 4.1E (on ModMii's download page 1, "60" and "4.1E"). If all goes well u'll be able to load the system menu (but not priiloader anymore) then just use modmii like normal afterwards to reinstall priiloader and other important hacks, but the risk here is that the solution of reinstalling the system menu uninstalls your lifeline (priiloader). It's possible to use dop-mii to install a new system menu without removing preloader, I haven't used it myself, but it's probably worth looking into (you can download dop-mii from ModMii's download page 2).
If you have bootmii installed as boot2, then u don't have to worry about the risks of losing priiloader or bricking, u'll be fine. And if you don't have bootmii installed as boot2, and shit goes sour, DeadlyFoez will be able to fix your wii no matter what as long as you have a nand backup.