Clutch vibration and clacking sound

Hello from a new member in Central NC. This past Saturday (5/30/2020) I became the proud owner of a 2003 Mustang, 3.8 ltr, 5 speed manual. The car has 157500 miles on it and I'm the 4th owner. On the test drive and on the drive home the car ran and shifted perfectly. Once home I got out the owners manual to look over the maintenance schedule and other items. One thing I read was the paragraph on clutch adjustment which seemed simple enough. Put the car (not running) in first gear and pull up all the way on the clutch petal, then slowly push the petal all the way down and you will hear a click and that's it. So I did it & when I drove the car the next day there was a vibration in the clutch petal when you took your foot off after shifting gears, there was also a clacking noise that disappeared if I just very lightly put the edge of my foot on the clutch petal. This started after I did the "clutch adjustment" as outlined in the owners manual. The transmission still shifts fine, no change in that, just the vibration in the clutch petal and the clacking noise. I have a Haynes manual coming next week and hoping that will shed some light on the matter, but thought that the experts on the forum could provide helpful troubleshooting advice. Thanks in advance.

Thanks for the bump and I'll take your advice about YouTube.

I'm in total agreement with you on replacing the auto adjusting clutch petal with a manual adjust cable assembly. I owned a 1982 Chevy S-10 that had a similar plastic auto adjusting mechanism that was also a PITA. Our son still owns the S-10 and it's currently deadlined because of that very same plastic part. The previous owner of my Mustang stated that the clutch assembly was replaced approximately 12,000 miles ago, so I guess the install may have been done incorrectly or inferior parts were used. For the short term I think that I'll replace the cable with a manual adjustable one and adjust it to eliminate the chatter (if possible) and plan to replace the whole clutch assembly during the winter months. Thanks for your suggestions Weendoggy, your website convinces me that you know what you're talking about.