The information that @jtsanders gave you is essentially a cut-and-paste of the factory procedure to remove the upper intake. It actually contains all you need, including torque specs. Make absolutely sure to replace those gaskets. Don’t try to save money and reuse them. It’s not worth it. they’re already compressed and might not seal correctly a second time, in which case you might have a check engine light and the accompanying lean codes
My thoughts as to doing the plugs without removing the upper intake . . . don’t take this approach. You might wind up damaging something
BTW . . . this is not “a very questionable design” on Ford’s part
On many transverse V6 engines, you have to remove the upper intake to do the plugs. Standard procedure. It’s not as big of ordeal as it may initially seem to be
Also, use the plugs specifically called for, in the owner’s manual. With the amount of work required, it’s not worth using some other brand, and maybe your engine “doesn’t like them”
Why don’t you check youtube . . . I wouldn’t be surprised if some guy filmed the whole procedure and uploaded it