Newby Replacing Immersion

Hi all
Increasingly I am seeing a leak from the immersion pockets on my 2000 and have got to the stage where I have no heating from the lower immersion.
I'm reasonably confident that I can shut the system down and drain it.
My question really is about replacing the immersion itself. I have changed thermostats before and that is very simple, but the physical process of removing and reinstalling the lower immersion is a little daunting.
Can anyone advise on any tricks etc that might make it easier?
I have purchased the right sized spanner and parts seem to be easily available.
Despite my surname being the same as the manufacturer, I don't get any discounts :-)
Oh and when it comes to refilling, it it plain water or does it need an inhibitor?
Best
Paul

Read through the posts on here ref your unit.
Also look on you tube.
There will be a video showing you / giving you ideas

Mike
MGC/H2O
Norfolk