removing stock stereo from '92 corolla. HELP!!

[rockthishouse]

I've seen the diagram here:
http://carstereohelp.com/stereoremovalToyCorolla4.htm
and removed the dash and everything. now I can see the 4 screws that's holding the stock radio in place. I tried just unscrewing the screws but i'm stripping them instead.. they won't come off!! I'm wondering if they have bolts in the back that hold them into place?? and if there is what can I do about it?

Also, is there any way to test if my new cd player/receiver works without plugging it in the car? Can I take it to a store or something? I have only two more days left to make sure that it works, after this time I won't be able to return it if it doesn't...
Any help is appreciated..

[Luc]

Use an 8mm socket and a rachet, and the 4 screws should come off. Any car audio shop should be able to bench test the radio with their DC power supply, but they may charge you. Otherwise, just install it with a harness adapter and test.

[rockthishouse]

what do you mean by the 8 mm socket?

(haha obviously i'm new)

EDIT:

if you mean something like this:

http://www.pelicanparts.com/catalog/..._cv_socket.jpg

do you mean using the socket for the stripped screws?
you know that the screws I'm talking about are philips, right?

[Luc]

That's a socket alright, but it's star-keyed. You just need a plain 8mm socket with a hexagonal opening, which can be picked up at any hardware store. The socket fits over the bolt, since the Phillips key is stripped.

[rockthishouse]

thanks.
I'll give that a go.