2003 honda accord problems?

I don't know if it has any relation but yesterday I installed a aftermarket head unit where the cubby was and added 2 subwoofer and an amp. Then when I was driving home my abs light came on and then my brake light. Then this morning it did the same thing and this time all the gauges dropped and didn't come on for a few mins. Then at lunch today it did the same thing but this time it didn't go back so I turned the car off and tried to start it but now it won't start. All the dash lights pop up but the car just clicks when trying to start the engine. The engine light has been on since I got it two weeks ago

Help is my master cylinder bad?

1994 honda accord ex

Problem: brakes iniital good, but then went all the way down, car did not stop

tried to fix: Bleeding the brakes, rear brake calipers were real rusty, tried to remove them but one of the bold in both sides was stripped so finally gave up.
Bleeded all 4 wheels, took out the fuse from the ABS

what happens now: brakes feel nice and tight, but once i drive the pedal goes to the floor directly, I'm not comfortable at all driving this way. Do you think its the master cylinder whch needs replacing?

If i replace the master cylinder do i have to bleed the wheels again (or just bench bleed the master cylinder). Please help, if i take it to a shop how much would they charge me excluding the cost of the master cylinder? (approx)

How much will the dealership charge me?

I have a honda accord 2005 ex, and I'm going, to be taking it to the dealership tomorrow to get it checked out & hopefully fixed. These are the things thats wrong with it:

- Engine light on (o2 sensor)
- Maintenance light blinks five times then cuts off (maybe oil change)
- CD button doesn't respond anymore so I got no working CD player (I don't really care much about it just wanted them to check it out)
- The key jams when I put it in the door and doesn't lock or unlock (really want that fixed I have to keep my doors unlocked)
- It makes bumping noises when I drive, as if one of the tires have too much air (that's not what's wrong with it, but that's an example of what it feels like, it bumps when ever the wheel turns)
- Wheels need to be rotated

These are the things that are currently wrong with my car. I've had it for about a year and a half and I haven't took it to get it checked for anything since I bought it used, when it had 70,000 miles, now it has 102,000 miles on it (I'm military and I travel alot in my car when I get the chance) But I also know nothing about cars.

How much do you think the dealership will charge me for all of this? What do you think I should do because I have an appointment with them in the AM