Warning lights

Start by having the charging system tested. The anti-lock brake system is very sensitive to proper system voltage and GM's generator has a very high failure rate. If the generator is defective, replace the battery at the same time. As they age, they lose their ability to dampen and absorb the huge voltage spikes these generators produce due to their design. Those spikes damage the internal diodes and voltage regulator as well as interfere with sensor signals for the many computers on the car. The old battery may still work fine in a pre-1987 car.