Apollo brake system

I am fairly new to Motorhome ownership. I purchased a used MH that had 4000 miles and came with a Blue OX tow bar system and Apollo brake system. I had the baseplate and breakaway switch installed by a local RV dealer on my 2012 Caddy SRX . The installer said they could not install the sending unit relay required to send the signal to the receiver in the MH because of the Caddys electrical system. I made my own and worked that out. I ordered a extra breakaway switch and extra plungers from blue OX using the number of the existing breakaway switch the dealer installed. They sent me out the extra plungers and a new switch that will not accept the spare plungers. And a few weeks ago my brake away switch fell apart. Turns out they used a hose clamp to fasten it to frame member instead of bolting it. I have the new switch installed temporarily until I get home. Now I have extra plungers that are useless . Next my Apollo brake system develops a air leak. I take it apart and find the air regulator filter housing is made of plastic and it's cracked at the drain port. Sort of suprised to find a plastic housing being used for such a important peiece of equiptment. Does anyone know if it's worth fixing this hardy used Blue Ox Apollo system or would I better off scraping it for something of better quality. The plastic vessel being used in a air system sort of scares me.