It's been years since I did the job. No short cut way to do it. You are in very tight confines as you already know, and long, skinny fingers are an advantage here. The task is all about getting the new part to press-fit onto the existing hose, so you try to use two fingers on one hand to leverage the hose and as many fingers as you can on the other hand to apply the necessary pressure to insert the new coupler!

I don't remember having to disconnect anything other than the affected part, but I might have damaged a bit of the firewall material in an effort to gain more working room.

I have short, chunky, (and bruised) fingers...this was not a fun project!

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2009 ML350 (106K) - Family vehicle
2001 CLK430 Cabriolet (80K) - Wife's car
2005 BMW 645CI (138K) - My daily driver
2016 Mustang (32K) - Daughter's car