Tips for Main water heater service

[Jennie]

Hi all,
I'm due to service my first Main water heater next week. I haven't taken one apart before, so I'm a bit apprehensive. The boiler is two years old, but the flame picture has a yellow tinge, so a good clean is in order.
Most of it is straightforward enough - until it comes to the funny three-point turn to remove the burner. I have the servicing instructions but could do with some tips.
The instructions say to undo the large union connection below the burner (taking care not to lose the fibre washer). So I'm thinking once that's undone, (and after also removing the pilot assembly,) the burner can come out. How tricky is it to lift the skirt of the heat exchanger to make space for it to get out? And getting it back in again afterwards?
Tips would be much appreciated.
Thanks everyone,
Jennie

 

[Pssst]

What model is it please?

 

[Jennie]

It's a Multipoint BF. I actually did the service today, but advice is still much welcome.
I couldn't get the burner out. I followed the MI - removed pilot assembly, removed test pressure pipe on the left hand side, undid the big nut under the burner. I then tried to push it up inside the heat exchanger to do the 3-point turn. However, the burner was too wide to fit up inside the heat exchanger. I tried, but couldn't find a way. In the end, I managed to access various bits of the burner in situ, so I could brush it clean. So I did the service, but still would have liked to get the burner out. I'd love to hear how to do it.
Jennie.