First off, since your on 3.41 OFW, update your console to 3.55 OFW! I do recommend Rebug, however the Rebug lite version
is best if you want homebrew, multiMAN, and a few other cool features. Now, before you install ANY CFW, Toggle QA. Use Rebug Toolbox if you must.
Do not go into factory service mode. In most cases, you can update from a 3.55 CFW to a Rebug CFW with QA. But since your doing it from OFW, Toggle QA and just install it.
If you are on a 4.XX CFW, you will be able to downgrade back to your original firmware, BUT you can only downgrade as far as your base firmware goes. If you happen to brick your console, you will need a hardware flasher.
Also, I recommend using Homebrew OFFLINE! Except for multiMAN STEALTH!