Vehicle not starting

Hey all. I have been reading about my problem and just want to get advice on the solution.

My 2002 Impala has not been starting the last couple of weeks. I did the wait 10 minutes thing and it has been starting. I took it to the dealership and they fixed the wires to the BCM (before I did any research).

Now my vehicle is flashing the service/battery/security light at different times. My radio gets locked and at times, my auto-headlights go off (so I have to turn them on manually). Also, my dome light stays on sometimes even though I attempt to turn them off (I usually just pull the fuse after this).

I don't know the age of the battery. I bought the car in 2007 and I have not changed the battery. I will be checking the battery today.

I believe it might be the BCM. I don't think it is the ignition switch since I am having "body" problems.

Are my assumptions correct? Thank you for your help.

Forgot to add...

A/C is not working and automatic locks do not engage either.

Start with a complete battery test and look at the cable and ground ends also.

Did all these troubles start after you got it back from the dealer? If so, I would take it back with a complete list of new problems. The dealer should fix what they appear to have broken. Remind them that, as an American taxpayer, you are a majority stockholder of GM.