Yep, any auto store has them for around $5 - $6, over in the speaker-wire/ stereo-accessories section. They are U-shaped hooks that insert into both sides of the radio and then you pull on them and it comes right out. I've heard of people making their own out of coat hanger, but I tried it and it didn't work at all. They actually damaged the internal clips and then when I got the real tools, I had quite a time getting it out.
the trick is to not push em in too far, just enough strength to put em in, then bend them both OUT (towards each seat) and pull out. Bending them pushes the clips in towards the reseiver allowing the radio to come out.
Forget about the nails. I tried using 4 rivets and it wrecked my friggin fingers so badly it took me a month to grow back new skin.
If you can't afford the $6 for the correct U-shaped tools, use the coathanger idea. After fumbling around with the rivets for an hour, I made the tool from the coarhanger and had the radio out in 1 minute and I didn't break anything.
If you're fully removing/replacing the radio unit you may need to put your stick shift into second gear for clearance purposes. I was installing a new bulb into my stock FORD radio as the bulb behind the LCD was burnt and found I couldn't work on the radio faceplate properly without moving the shifter out of the way.