I recently changed the PVC valve on my 1996 XLT with the 4 cylinder 2.3. After struggling to find the thing myself and after reading a number of posts about the trouble everyone seem to have, I decided to try and provide a picture of where it is and what I did to be able to get my hand on the thing.
Using the following image, here are a few hints:
First, 'A' marks the location of the PVC valve. It's hidden below the spark plug wires on the drivers side.
Next, by taking out the bolt marked 'B' you can tilt the black cover back a bit and give yourself some precious room (you'll need it).
Letter 'C' marks where some wires are clipped in. You can pry this clip out and move the wires a little bit out of the way.
Letter 'D' marks an electric plug that you can unplug by squeezing both sides and pulling it off. Should come off easy. Move it out of the way.
Letter 'E' is the spark plug wire. Remove it carefully. Twist and pull or better yet if you have one of those fancy pliers that grabs the boot of the wire, use that. Just don't pull directly on the wire. Only pull on the boot. When the plug wire comes off, move it out of the way.
Letter 'F' marks the clip holding the spark plug wires. You can open up the clip and move the wires around to give yourself a bit more room.
You now have the area opened up about as big as your going to get without removing engine parts. If you can get your hand in there you can remove the PVC valve fairly easily. Mine was changed after 100,000 miles and it does not seem to stick (at least mine didn't).
Install the new PVC valve, and reassemble in the reverse order. Look everything over one more time and start it up.
You should be good to go.