I humbly suggest you read through your manual, as well as the FAQ site here, Main Page - BlackBerryFAQ
1-Go to Profiles, scroll down to ADVANCED, and edit from there.
2-Your Carrier will know that. Some you can dial like #MIN# and get an accounting. I believe that works with TMo, and mytmobile.com has that info as well.
3-Email the picture to yourself, open attachment and save. Go to Picture Viewer and open that picture, SET AS WALLPAPER. You can also transfer jpgs from Media Manager in your Desktop Manager.
Good luck, welcome to the Forums.