Concerning your spark plugs:
Concerning the cam phasers:
https://www.youtube.com/results?search_query=5.4+triton+3+valve+camshaft+phasers
Do the research to get a good understanding of what is involved.
As to what to do ….
That comes down to your budget, skills required, tooling available and time investment.
Also the basic mechanical condition of the vehicle IE. transmission, brake system, front end, suspension etc.
Meaning if you do the stated repairs will the vehicle keep costing you in repairs of other major components a short time later.
Can’t say in your specific case if it is worth the investment or not.
Only you can make that determination.