I have 357,000+ miles on my 2005 2.3 never touched anything inside the engine,,, yet.
Duratec 2.3s don't have traditional tappets. they have cam followers that look exactly like an upside down bucket. they go between the cam and valve tip. to adjust the clearance you replace the bucket with one that has a different thickness.
replacing them is easy,,,,
after the cams have been removed,,,simply lift them out of the head.
I'll try to get some pics up soon.
edited....
the head is a 2.5 Duratec from a 2010 Fusion, same as a Ranger 2.3. the cam followers drop into the holes open side down. then the cam goes on top.
I couldn't locate any 2.3 cam followers, the ones pictured are from a 1990 Yamaha 3.0 V6,, same principle but they use disks set on top of the followers to adjust valve clearance, we get to swap out the whole follower.
the Ranger 2.3 Duratec followers have a totally flat top surface. the thickness of the top determines clearance, they are available in lots of sizes.
to check/,adjust the clearance you first measure the actual gap, then compare it to the desired gap, note the difference if any.
then remove the follower and measure it's thickness,,, if you need more gap get a thinner follower, if you need less gap get a thicker follower.
the follower may be worn, that means the stamped thickness isn't accurate, measure it for best results.
for building a head from scratch install cam and measure between cam and valve tip, subtract desired clearance to get follower thickness.