I have bought a refurbished controller unit for my Aqualisa Quartz gravity pumped unit. I am fine with the electrical connections but wondering how exactly I remove the old unit from the inlet/outlet pipes. Looks like they go into pushfit plastic isolation valves but unsure how to detach from this type of valve. Initial thought is that the white collar is pulled back and then unit can be removed? For install of new unit is it just a case of pushing inlet/outlet into the isolation valves? Does anything need to be replaced? I have attached photos of current installed unit and the one being delivered. Not a great fan of working on anything involving plumbing so just wondered how fiddly this is expected to be/if these tend to be stiff to pull off or likelihood of joins leaking, thanks.