1997 Cadillac Deville warning lights and heater will not bl

Heater problem
1997 Cadillac Deville V8 Automatic 138.50 miles

I have a 1997 Cadillac Deville Northstar and I have several lights. One is the abs/ traction control light. One is the service steering column and the service brake swithlight. Sometime the brake light comes on also and flashes. The car sat up a while not being driven and now all of these lights is comming on. Can you tell me what these lights mean and wil it harm my vehicle if I keep driving it. The water pump and gas pump were recently replace because it was hard starting in the cold morning and the low coolant lights kept coming on. I thought replacing the water pump would make the car heat up. Only heat up through the defrost being on 90 and hi. Will not blow out of vents even on 75 or 80. What is going on. I cannot not afford to fix this car if it keeps getting worse. Is these problem expensive