first off
WELCOME TO THE SITE !!!!
Your dead on the right track
oil, filter, air filter, pcv valve, spark plugs, spark plug wires, cap and rotor
I always used the ACCEL distributor caps in my (former) 98 Ram because they had one with brass inserts, (better electrical connections) but NAPA has one like that as well
as far as spark plug brands go: thats as opinionated as what kind of oil, but again my choice was always to go with NGK (specifically I used the ZFR5F11's)
a lot of people say when they switch to NGK, their idle is a lot smoother
Seafoam is another great idea - but do it BEFORE you change spark plugs as it has a tendency to foul plugs
(do a search here for seafoam, its a popular subject)
and I used Royal Purple syn engine oil and had some in the rear diff as well ...
always stuff with Mopar brand AFT4 in the tranny fluid
and while some people don't always agree with this - when I had higher mileage vehicles, I would run a can of engine flush thru to get all the old gunk and varnish cleaned out... again, some people think this may dislodge something and may lead to other problems, but it never happened with me ...
here's one other thing, (not part of a normal tune up, but offering as a thought) I had the radiator professional cleaned out - back flushed and the works
One last question: is the cat converter original ? How many miles on the truck ?