You could do it yourself with no welding expertise, by buying a replacement axle with the brake plates already installed. The plates are for mounting the disc brake assemblies.Otherwise, you will need to buy the plates and weld them on, welding will need to be good. All the rest is just easy bolt together, apart from possibly needing to drill holes to mount the over-ride brake assembly to replace your current tow hitch on the trailer.
So you will need an axle with plates attached, two mechanical disc/hub assemblies, an over-ride brake coupling, the adjustment bit with roller for overall cable length adjustment, and some steel cable to run between the brakes and the coupling. Most trailer specialists will sell kits, unfamiliar with the one you mention, as I am in WA.