@Wever,
there is virtually no risk to updating your boot2 version. The only risk is losing power during the operation, but it's a quick installation IIRC. What can make updating boot2 dangerous is when people don't realize that it's overwritten\uninstalled bootmii@boot2 and they do no reinstall it before attempting some risky business. So basically, if your wii has bootmii@boot2, and then u update your boot2 version, you should immediately reinstall bootmii@boot2.
Anyways, to go about this just download the version of dop-mii available on ModMii's download page 2. Launch it on your Wii, and I can't remember exactly what the menu item is called but there will be something listed there to update your boot2 version to boot2v4 (you might need to select an advanced menu or something before u are able to see it). But basically just use dop-mii to update your boot2 to v4, it will get you to confirm by pressing an odd button combination. And that's it, you should now be running on boot2v4. Make sure to reinstall bootmii@boot2 (if applicable) and now if you ever accidentally do an official nintendo update, your bootmii@boot2 will survive the update.