"how can i tell how bad it is" - depends, do you see a gaping hole? If you do then its bad.

Heres a video
http://www.youtube.com/watch

Sand blast rusted areas, prime and paint,,,,if u hv holes, fix holes first

To replace the chrome plastic cover, you have to purchase the ignition lock cylinder, which comes with the chrome piece. A locksmith can recode the new lock cylinder to work with your original keys. Proceedure for replacing ignition swich cylinder - Disconnect battery ground cable.
On models equipped with tilt steering, unscrew and remove tilt wheel handle and shank.
Remove three lower steering column cover screws, then cover.
Turn ignition switch to On position.
Place suitable 1/8 inch wire pin or small drift punch in ignition lock cylinder access hole, then depress retaining pin while pulling lock cylinder rearward to remove.
Reverse procedure to install. Lock cylinder is fully seated in housing when pin snaps into access hole.

Any applicable trouble codes? What about the dimmer switch? There is a lighting control module behind center of dash.

sounds like you may have a bad fuse, or the wiper motor has a short or bad ground in it. im leaning toward the latter.

This link will help you to negotiate with the local auto repair shops for a reasonable prices.

http://www.automd.com/negotiator/

Check the power window circuit breaker. When you try to operate window, feel of the circuit breaker, can you feel the vibration, when it clicks? Does the CB feel warm to the touch. Sometimes with a faulty window motor or faulty wiring, it can trip the breaker, then, none of the windows will work.

You should take your vehicle to a service shop. To fix and identify the fault of why your airbag light come on.

And if possible check out the TSB below for your vehicle.
2002 Mercury Grand Marquis Air Bags Service Bulletin 326848

NHTSA: Action Number: 10008579 Service Bulletin Number: 326848

Report Date:
Sep 02, 2002
Component:
Air Bags


Summary: Restraint system-air bag deployment strategy with advanced restraint system. *mj

1. Access the vacuum hose connector at that back of the EATC module in the dash (the control head). Check the Black hose for full manifold vacuum. If not present, repair the leak between the engine and the EATC module.

2. If the BK hose has strong vacuum as it should, check the White, Yellow, Red, and Blue hoses to verify each hose holds vacuum if applied with a hand vacuum pump. Repair any leaks as needed if any hose does not hold vacuum.

3. If all hoses test OK, use suitable fittings to jump the Black hose to the Yellow, Red, and Blue hoses with the engine running. This should cause the air to come out the panel vents. If it does not, check for any binding mode doors and repair as needed.

4. If all vacuum hoses and mode doors check OK, check power and ground to the EATC module. The powers are pin 2 Red/Yellow and 16 Brown/White of C228a (the Gray connector at the EATC module) and the ground is pin 3 Black in the same connector. If the powers and grounds are OK and there are no codes, suspect a bad EATC module.

You should check the fuse block under the instrument panel on the left side of the dashboard. A blown fuse can be confirmed by visually inspecting it.

Can you say for certain that you lost all these 3 things at the same time? Check fuses 21, 23, 27, and 37 in the interior fuse panel. Not only check the fuse by visually looking at each after removing each, but also by checking for battery voltage on both sides of the fuse with a 12 volt test light. I will assume you know how to use one, very easy, $10 tool. Update me on the status of each fuse.