1992 Chevy Lumina soft brake pedal

HI I recently noticed that the brake pedal goes soft after 1-2 hits but after pumping it 2-3 times pressure is built up again... anyone know of any issues with this? Could it be a brake booster? If so, is this tough to replace for a doityourselfer with limited experience?

If there is no loss of brake fluid, a sinking pedal that can be "pumped up" is a bad master cylinder. The bore has worn and is allowing fluid to escape past the seals, causing the pedal to sink. Not to difficult, the most technical part of the job is bleeding the system of air when you are done. A bad booster will cause a hard pedal/high pedal effort, like an old car with manual brakes.