1990 Chrysler Imperial crysler Imperial ABS brake problem

Hi,
My ABS light, anti brake light comes on and off when driving the car. Yesterday when coming home
the car was stopping by itself. When I parked the car the front wheels were hot. I bleed the brakes.
Im thinking it's the ABS hydraulic boost? It's a Bosh When looking on-line my other half came up with a pump by bosh for 450.00 and the full assembly for 950.00 Not sure where to go.
Was also going to check the brake lines. Any thoughts on what to check? Please give me a list of what to do
and what to look for.
Also what to replace?
Thank you
Jesse