That pass thru thingy on firewall on my Volvo.

Are you talking about those bulkhead fittings in the firewall? If so, they are not bad to change at all. If it is leaking outside in the engine compartment, just unscrew the old half of the fitting and screw the new piece on that and you should be good. If it's leaking inside the cab, you have to take the plastic piece out closest to the door. It is easier to take the bottom bolt out of the grab handle and push the the tilt wheel down when you're ready for it to come out. Hope this helps.

 

yea i replace mine is not difficult just make sure you reed those numbers on the new one because the new part has been change you have to swap some of them.even the new one will leak a little .

 

We have changed a few of them. You will need some skills, and you need to write down where things are because some of the lines go in a different location. Don't try to go on memory. It helps to have two people too.