AAZ scrap yard injection pump, any prep before install?

[Faulty Logic]

I pulled my pump a few days ago, and changed a few seals that were leaking (cold start assembly, and driveshaft seal)
Reinstalled the pump with a bunch of new parts (timing belt, tensioner, waterpump, t-stat, TDI alt pulley, idler's)
Everything went smooth and the pump set up perfect and worked really well.

Two days of driving and the pump is leaking again, (this time its the big O-ring between the distibutive head and the pump body)
So i went to a local yard and picked up another pump, really clean, bagged and tagged on a shelf with low miles. Now i want to install the new pump, while i rebuild my original pump from the ground up.

The new used pump is full of old fuel still but turns over well, is there anything i should check prior to install.........or just flush it with clean diesel and slap it on?

[Andy@React]

assuming you aint gonna take a couple of years to rebuild your old pump you may as well just slap it on!