The best way is to download the applications like mobile shell from your PC (called CABs, because their file extension is .cab) rather than using the cellular network which especially on a limited Page Plus data plan would be a disaster. Also keep in mind that Mobile Shell costs $30 when the trial expires. Go
here and click Download CAB, then save the file, plug in your phone to the PC and copy it over. When connected, the phone will show up as a separate icon in My Computer and you can go there to browse the files on the phone. I recommend using the My Storage folder which will place it on your 8GB internal memory that won't be erased when hard resetting or flashing a ROM (but don't get too far ahead of yourself yet).
Then on the phone, open File Explorer from Start menu and browse to the location of the CAB and tap it. It will then install and you may need to restart.
To shut down the data connection, tap the Ev or signal strength icon and in the pop up bubble choose Wireless Manager. Tapping Phone will cause it to go gray and the status will change to Off. And no, you will not be charged for using WiFi; it can be activated the same way.
If you need any help with any of that or anything else, please post back. I'll be watching this thread like a hawk since there's nothing else going on in this forum.
A few more things: Modaco would look a little daunting because there's lots of threads with terms you probably don't know yet. The
Omnia Upgrades section here is very simple to understand though there's not as much activity. You will find Lioryte's ROM there as well as a couple of others and even a First Time Flashing guide, so it's a good place to start. PS before you start flashing, most roms are based on what is called "CF03", the first software update, so you will want to have this on your phone before you even consider making any modifications. Go to Start > Settings > Version or open up your phone dialer and press #43574357*. If you see CF03 in the first line, you're good, otherwise you will need to install it. But stay with the stock software for at least a while to get used to it. The leaked 6.5 versions are very nice and I prefer them over 6.1, but there can be random bugs and weirdness in them and so your experience may not always be quite as smooth. Two things I notice are the touchscreen sensitivity is a bit less than stock, and some actions in the stock software feel a bit snappier, but don't let that turn you off from eventually flashing.