I tried this and while it worked fine, I decided that I preferred my previous way of just turning on MMS and 3G when I needed. HOWEVER, now that I've uninstalled Network, I no longer am able to access my data connection even after I change the settings under Mobile Networks. I am currently recharging my battery so I can do a Repair using PC Companion. *sigh*
NOTE: The developer of the app makes a disclaimer saying that some users have reported this to happen to their phones.
EDIT: Once I got my phone charged up passed 50%, I plugged it in to the computer to use PC Companion to repair the phone. I decided to check my data connection one last time before I repaired just in case I would have to reinstall my apps and lo and behold, it worked. So maybe there is some sort of timeout period or whatever after uninstalling that app? Anyway, my 3G/MMS is working again.