There are some things that you just change when you get a chance, and the timing set is one, unless you know it was changed on a previous trip inside the engine. Oil pumps are the same way IMO, but that is not coming out with a cam swap of course...
Valve springs and seals are parts that should be upgraded from stock 1st chance one gets.
Replacing the cam changes that "should" to a "must".
So, timing set, gaskets, valve springs, and valve seals.
Those are your minimal changes, assuming stock parts that you do not know for sure have been changed in the last 18 years.
A large cam or certain springs can often require aftermarket locks/retainers, but that is subject to what the cam and/or spring manufacturer says. I would probably get new locks and retainers because they don't cost too much, and you'll probably need to get rid of the exhaust rotators anyway, per cam/spring manufacturer.
If you don't remove the heads for anything, and don't install any other specialty parts, such as rocker studs/guide plates, you can reuse your pushrods. If the heads come off for any reason, the pushrod length requirement should be confirmed.