OblivionLord

Would it make a difference as long as it fits? I was only able to get the DX since that's all they had on hand because I need to use the car tonight. I also had to walk to the parts store for it late at night.

A-series

At the place you got it, they should be able to find out (pull it up on the computer) whether or not it's the same PCV valve for those two trims... or maybe they did and you know it's different, which is why you're asking h:

Sometimes different trims (and their respective engines) will share the same PCV valve, sometimes not. They usually don't look much different and will fit even if it's not the right one, but they specify different versions for a reason. Running the wrong kind for a short while isn't going to cause damage, but it might not allow the same flow as it's supposed to.
If you're in a pinch, you could drive the car without a PCV valve if you had to, until you could get the right one. You don't necessarily need to buy one, knowing it's incorrect, until they can get you the correct type.

OblivionLord

The DX version has the tiny elbow at the end which you can snap on or off and essentialy it looks the same as the EX. However the tip at the end is slightly smaller on the DX and when I say slightly, I mean really slightly. I connected it and ill have to wait a week or so to see if there is any pressure buildup coming out of any gaskets or what not.

So far so good

A-series

^if it's different, I'd suggest you get the correct one when you get a chance. I believe for your car, like mine, you can get them cheap, around $3. For some years they're $15.

When I first got my car it had the wrong type, and I replaced it with another of the wrong type. For some reason, the wrong kind was in the packaging for my model. When I finally put on the correct type (it matches pics of the oem one) I noticed a decrease in oil consumption.
If you blew/sucked air through them you didn't notice much difference, but with the car at idle, I changed them w/out plugging the valve into the grommet, just into the manifold hose. The correct one sucked noticeably more air.

schuylkill

I have a 1998 cx with D16Y7 engine. I replaced the valve and couldn't get the new valve to really press into the grommet, it's more like pressed against the grommet. Is this correct or must it be forced into the grommet?

The old valve came out easily from the grommet but I didn't really notice how far it was inserted.

A-series

If it's the correct type, it will go into the grommet to an extent. It might help to twist it back and forth just a little as you're pressing it into the grommet. If it's noticeably larger on the grommet/crankcase end, than what came off, I'd get the correct type.
If that's not the issue, you could try applying a small amount of clean engine oil to it so it slips into the grommet easier. I'll assume the problem isn't that the old valve broken upon removal and part of it is left in the grommet, as you'd probably notice that.