Although I know nothing about these things, I have looked this up in my VADIS software for you. Apparently there is a 5/8" Key (part number 999 5472) that is described as a Spring Locking Connector A/C Pipe (or quick release connector puller) that is used. Diagram looks like a sort of cylinder with a hinge on it with a hole in the middle. I assume it clamps around a hose or pipe. Hope this helps.

Specific instructions say:
Disconnect the pipe couplings at the compressor
Release the quick-release connectors on the receiver/drier (N8) (This is where you use the tool).
Remove the cover from the righ-hand headlamp
Remove the screw from the bracket for the receiver/drier
Remove the air baffle (2 screws).
Then, left the receiver/drier upwards where the bracket is hooked at the side member.

When replacing the receiver/drier, the new unit must be filled with 90cm3 of new oil. I suppose the rest will be done by the company you found and doesn't need explaning here.

Good luck and let us know how it goes.
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1998 S70 T5 Emarald Green Metallic, 2004 V70 2.5T Ruby Red, Previous Owner of Black '94 850 Turbo Wagon