KM, I'm having the exact same issues: the unpredictable lock-ups, the "phantom rebooting", and like you I'm on Gingerbread and never got ICS. To be honest I think this phone is no longer being seriously maintained by Sprint (apparently there were multiple problems the last time they tried to roll out updates to ICS, and they just don't think it's worth their time anymore).
One trick that may help you in the short term is to reduce the size of the unmovable bloatware. Reducing a 10MB app to 700kb is a great way to free up internal memory space and (maybe) reduce the weird problems you're having.
1. Go to the home screen, then into Menu/Settings/Applications/Manage Applications.
2. Then click the "All" tab.
3. Hit the menu softkey here and select "Sort by size", which will show you the biggest programs first.
4. Scroll down to the first app you don't care about (usually Asphalt, Sprint Football, etc) and tap on it.
5. One of those buttons on the screen, at the top right if I remember correctly, will be "Uninstall updates". If you do this with the bloatware I've found that this significantly reduces the app's footprint, even if you cannot uninstall it completely.
Hope those steps help!
Regardless, I'm thinking about rooting the phone, but like you I don't have a lot of experience with it. I'll probably follow the instructions on Cyanogenmod's website:
Samsung Epic 4G: Full Update Guide - CyanogenMod Wiki
If I have any luck, I'll post back here with tips.
If I have bad luck (!) I'll probably be jumping ship to the Galaxy S3 like so many other people. FYI, the SGS3 will be $50 on Black Friday at Sprint stores (and possibly other stores too).