It's a pity that Dometic do not include this advice in their instructions, at least they didn't in 2008, perhaps they do now.
As I understand it......the Dometic unit has no regassing point, and anyway there is nobody in UK licenced to use the chemical involved.......this information was supplied by Dometic themselves,so I assume it must be correct.
So if the unit fails due to losing the gas, the only option is to replace it. Ours failed after 3 years so Dometic eventually agreed to replace it before we went down the Sale of Goods Act route, but it took over a year to get a resolution.
The unit itself is very effective in use, and ours was/is not noisy in use as heard from outside. It would not keep the neighbours awake, but is noisier inside the van, so we would not use it at night. Best way to use is to have it keep the van cool all day so it never gets too hot to start with, then turn off overnight.