Congrats on your Challenger purchase.
Be very careful of the new origonal looking prop valves. There have been problems with them in the recent past. I heard that something internally was machined wrong and was restricting the flow. Last I heard, they hadn't gotten the problem fixed.
If your brakes are working properly and your only complaint is the leak, just replace the O-rings in the prop valve. There are three fittings that can be removed...they all have O-rings on them. I beleive the large fitting has a spring behind it so be careful when removing it.
Take the O-ring to a parts store and match it up to one in their assortment. Make sure to tell them that it is going to be exposed to brake fluid incase you need a special one.
I would clean the valve really good and hit the brakes a few times to verify which fitting is leaking. I woundn't disturb a fitting that is dry if you don't have to. You can always buy a generic valve if you are having other problems but I'd start by replacing the bad O-ring.
Good luck!
