Front Discs can be very easy to work on. (weirdly, when it comes to vehicle mechanicals, the only thing I really used to do on my own vehicles ARE the brakes!)
Rear Brakes can be far more awkward though when they incorporate the handbrake mechanisms. I don't know if the Ducato rear brakes need a special 'wind-back' tool like vans such as the VW Transporters do? If they do, it is tricky to work on them properly without those. (WITH the tool, which is cheap to buy anyway, it was pretty easy).
I had to have the rear brakes done on my Ducato around a year ago and it was not cheap

. But front brakes really are much more straightforward and you should not need to pay
that much for new discs and pads even with fitting.
@marchie , I would get a quote from a couple of places to get an idea of prices. Even replacing Calipers does not take long to do.
PS. I don't know what you usually do about brake fluids, but it should really be replaced every two years (typical charge is £25 I have found), so if you have not had this done in the last two years, I'd recommend getting it down at the same time as the brake work. Refreshing the fluid at that time makes most sense, esepcially if you DO end up with new calipers. They would charge you for some new fluid anyway to top up, so just get the lot replaced.