Security message is on display and car will not start

What is your question?

Recently, check engine light came on and was flashing and the car was idling very very rough. Drove the car home - barely made it. Brakes were almost non existent. Checked code and multiple misfires were indicated. Had car towed to local shop. They found lots of oil in and around all plugs and boots. They said it was because oil around plugs was causing misfires and rough idling. They replaced the manifold gaskets, plugs, coils, boots and grommets. Tried starting the car and still ran a little rough, then cut off and would not re-start - a Security message came up. Now car will not start or turn over.

What makes this problem better or worse?

Changed items listed previously, and now got Security message.

How long has your 1999 Lincoln Town Car had this problem?

A couple days. Happened all of a sudden while driving to work