I removed the stereo on a 2001Lincoln LS V8 now it won't start.

That shouldn't be the problem. Maybe it distracted other system part.. I guess instead of waiting for answers here just google it.. or like go for reliable-store.com. u can simply get answers to your questions there..

The car or the radio wouldn't turn on? If it's the radio you need to get the code for it it's security locked just in case it got stolen. If it's the car it maybe on a security lock down too. Put the radio back or check you might have a blown fuse.

That is because the entertainment system is part of the security system, you are locked out.