If it were my PUP and just bought, I would pull the hubs, inspect, remove an rust, check remaining brake pad thickness, etc. etc. I would then adjust the front cylinder. Lots of Y-Tube videos on how to inspection brake hubs. And while the hubs are off, I'd replace each hub's seals and re-grease each hub as well.
If wondering, I'm not a fan of surge brakes. For me, I've have much better luck with full electric brakes. If the existing brake hubs, brake pads or compression cylinder needs replacing, I would simply convert to full electric brakes. I find full electric brakes easier to adjust, easier to understand and easy to buy parts as well. Especially when STAR brake wiring is installed. re: http://i178.photobucket.com/albums/w...iring-Star.jpg
If wondering, I have 3 x trailers with full electric brakes and never had breakage problems with them. Normal wear and normal annual re-greasing.
Hope this helps.