This may already be posted, but this is apparently the proper place:
I use Handcent for SMS/MMS. I found out the hard way not to remove the MMS.apk file, the stock text messaging program. You will not get any obvious problems and regular text messages will still work. But you will not get any Multimedia Pictures, Video, Music, etc. If you are signed up for Boost Media Mail, you will see them there only.
If you do delete it, put it back in the /system/apps directory using Root Explorer or something similar. Then reboot your Prevail. Any new MMS will then start going to both Boost Media Mail and your phone.
I hope this helps some other dummy like me.