Now what do I do?

Yes, I'm a newbie and this is probably really simple, but I've been searching FAQ's and this forum and cannot find the answer.

I created a 30 X 30 platform and was learning about altitude when I think I accidently set the "Z" elevation to 2 and my platfor vanished - I'm guessing into the ground. I wasn't worried about it at first as I had a copy, but then I noticed that it shows up on the mini-map in game (I think). That makes 9 prims on my land which I am unable to use!

So I have 2 questions;

1. How do I find out if it's really there?

2. If it is there, how do I delete it?

Thanks in advance for any advise!

For things buried in the ground the easiest method is to turn off surface patch rendering, which makes the ground go away:

CTRL-ALT-D to turn on your "debug" menus. Then:
Client --> Rendering --> Types --> Surface Patch

ooooooo - neat stuff in those menus...

...thanks - that helps a bit, but I dug a HUGE hole and I'm still 105 meters up - I can't see that far (I think I set it's elevation to "2". Is there a way to see farther? (Does any body sell magnifying glasses or telescopes in SL )?

Go into Preferences and increase your draw distance and then go back into the Client menu and check "disable camera constraints" that should do it...

Thank you very much for your help, Isablan. I'll return the favor by helping someone else when I know more about how SL works.