4. Can my media card be used for songs, pictures, and videos or do I need separate ones for each?
One media card is all you need. When it is formatted for use in your Pearl, sub directories are created for different media types. They are for your convenience, Media Player will find them no matter where you put them.
question 2:
Goto Options>Screen/Keyboard>Key Tone. select "on" or "off".
question 3:
Absolutely, Yes.
question 4:
Yup- you can fit it all on one- and as jenaywins mentions, bigger is better.
I'd try and stuff as large a memory capacity in as I could. They're fairly cheap too.