I looked at my '08 and those phaser valves ain't coming out without pulling the valve covers. But I believe some earlier years could be changed with the covers on.
I flip flop between being a hack, and wanting to do it right.
Most of us who do our own work do...
My 2010 Explorer had a bout with a rough idle, and then threw an bunch of phaser codes for both sides. Two times it did it. After trying to wish myself that it was simply a loose electric connector, glob in the oil, alternator diode or other silly stuff, I manned up to the likelihood of it being a chain guide or low oil pressure and bought a $1300, 4-year powertrain warranty (last night). On the chance that the cam bearings are shot or there's crank end-play, i didn't want to pay for a new motor. The Ford has 90,000 miles and I bought it a year ago. Hey, my oil change could have been its first for all I know.
I'm looking forward to hearing that you had good luck with this.