How can you enter your locked 1998 Aurora when the key nor the remote will work?

I hope that answer - "use a rock or brick" - was supposed to be a joke. You're telling someone to break a window that will cost almost $1000 (parts & labor) to replace, just to avoid paying a locksmith $75 to open the vehicle? Lubricate the lock liberally, for starters. When people use the remote exclusively for unlocking the car, the grease in the unused locks hardens up from lack of use and the lock wafers won't work properly otherwise. Work the key in and out several times to loosen up the grease and then try to turn the key. If the remote stopped working, replace the battery. The two halves of the remote will pry apart like a clamshell and reveal a disc battery (probably a 2032) that costs about $3. Radio Shack will replace it for you for a small sum. If you lost the key altogether, a locksmith can make a new first key for about $250. It's more expensive because the key has a chip in it that the vehicle's onboard security system must see to allow it to start. Don't whine about the price, either - it wasn't the locksmith who lost the key! A dealer can make a new first key, too, of course; expect to pay about $400.