A lot of people have trouble getting the components separated. If that's the case, or if you didn't want to bother, just go with a simple upgrade. Get a basic Fabco NV-55 and two 10-32 NPT to 1/8" barbs and run it inline. Keep the stock valve all the way open. You can even keep the stock bubble counter if you like.
However, I'm of the opinion that when it's time to upgrade a single component on those prebuilt units, it's time to upgrade the entire thing. I guarantee that even if you upgrade the nv, you're still going to be unhappy with the rig.