3XW, replacing collector box with Delkevic

[Storleer]

So I need to replace the collector box in my 3XW, will be buying this: https://delkevic.co.uk/yamaha-fj1100-1200-84-96-stainless-steel-exhaust-collector-box-oem-compatible.html?fbclid=IwAR3osZrbs0L0ipscAFV2v-htX6EagZTSDMNXq-dQnaKHYiGc9Fjbm-e9t_E

Procedure: remove the cans, off with the old collector box, then wedge the new into place, then put cans back in?
Or do I have to remove header pipes from the head?

Was thinking of only buying the collector box as the stock headers look to be in good shape.

Sorry for this newbie-question, but I have some not-so-fond memories of refitting the entire exhaust in my previous FJ1100 some years back, so I was hoping that this is as simple as i believe.

[X-Ray]

I've always found it easiest to have the collector box loosely bolted on, then attach and tighten the headers, tighten the collector bolt, then slip on the mufflers. But others might have a better way of doing this too

[FJ_Hooligan]

I think you'll find it easier in the long run to remove the headers.  Keep them in order, they are numbered