brake proportional valve

Usually, no it won't be too difficult but you may run into problems getting the lines out if they're rusted up. Soak everything in PB Blaster before you try to loosen the brake lines up and use a line wrench, not a standard open-ended wrench. Any auto parts store should stock it or be able to order the part. Make sure you bleed the rear brakes after you're done and never let the reservoir run dry.