To remove the factory head unit you need a pair of keys as shown below. I got mine at a dealer but you can find them on Ebay or other sites.
When the stereo stops working and you can't get it back to life no matter what, try disconnecting the battery for five minutes. For me that works every time ... but I only go to this extreme when all else fails.
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=140270362732