I can't figure out how to access files that were downloaded to the SD cared. I saved some pictures from the internet to use on my lock screen but I can't find a way to access them.

Also, what is the "Gallery" and how do I find it?

Try Alums, that should list the pictures on your SD card.  If you want to search for other files types you can download an explorer, such as AndExplorer.

I "mounted" my sd card thru the usb connection on my computer to move items around and create a few new file folders on my sd card.

I found the downloadable free android app "AndExplorer" very helpful because of it's flexibility. Better than the other file explorer I tried.

I'm assuming from home screen you tried 'menu', 'wallpaper', 'home', 'albums' ,('camera shots' or 'all photos', or 'wallpaper') to choose your favorite...

Wallpaper just looks at the ones in internal memory I believe.  The albums choice should show you all the pics on your sd card by directory.

C'mon, guys. If it was that simple I wouldn't be looking for a solution. I'm not tech ignorant. I need some input from someone who is an expert on this phone.

Dude, you get what you pay for.  If you want an "expert" I suggest you hire one.

First of all, young man, I'm not  "dude" I'm a lady. Second, your sarcasm is not welcome, nor is it appreciated. In other words, "dude', KMA.

Sorry Dudette then, ;-)

Look, just trying to help and without actually being able to see what you are doing it becomes a shot in the dark kind of thing.

So, some questions that may help narrow it down.

1. Have you connected to you phone via USB with your computer and looked to see where they are stored on the SD Card?  - They might be in the download dir, but could be anywhere.

2. Are they in a JPG format?

3. Are you using "Albums" or :"Wallpaper Gallery" to look for them? - "Wallpaper Gallery" I Believe just looks at you internal memory for JPGs and not the SD Card.  "Albums" scans your SD Card and presents all found pics by dir.

If none of that helps, then please list the steps you are doing to "try" and change the wallpaper.

go to Settings.... Applications ..... manage applications .... SD card