Yeah - the *best* advice I can give would be to *only* use OEM water pump and timing chain tensioner. Have read of way too many problems in very short time on aftermarket 2.7 tensioner and water pump. Haven't heard of any problems with the chains themselves. Ebay is fine for any of it, but *only* if the parts are genuine Mopar, preferably from a Chrysler dealer. OEM will ensure that you get the much improved later water pump design (beefier bearings and much better gasket design). Aftermarket is a hodgepodge of quality *and* old and new design - avoid no matter how good the pricing.
OEM has had kits - may or may not include chain tensioner and water pump. The kits are a good deal price wise, so get the most complete one that is available so you don't have to add individual parts (like water pump or tensioner), which aren't priced as well individually as in the bundles.
There was design change on the tensioner for 2000 MY, they are not interchangeable, but applications lists should indicate the right one for your 2004 (you should see 2001-2004).
Don't worry about the secondary chains and tensioners - no one ever has problems with those, they don't wear out.
One last twist to add a one more level of complication to your decision: They redesigned the chain (different pitch) when the LX platform came out with the same 2.7 engine. You can get an OEM kit that includes the chain and all sprockets (for both cams and crankshaft) - may or may not come with water pump (also would need the finer pitch sprocket). If no pump, you would need the pump that comes with the sprocket for the later (post-LH car) chain design. That is a nice way to go, though a little extra work R&R'ing the crank sprocket. *IF* you do go that route, consider replacing the oil pump since the sprocket has to come off for that too, but that's optional - they generally don't give problems. Not sure if the tensioner is different between later year LH and the LX platform. Unless you can find that out one way or the other, safe way would be to get complete kit without the tensioner, and buy the tensioner separately (kit may not come with tensioner anyway). I think all kits will include the chain tensioner arm and chain guides (only one design to worry about on those).
I dumped the whole load on you at once.
Oh - make sure you remove and discard the old water pump gasket. It can appear to be part of the block - installing a new pump gasket on top of that will create *big* problems. Some people made that mistake - I almost did (actually I did, but caught the error before I got things all the way back together, but not before ruining the timing cover because of it).
'98 LXi - Later Concorde gages (black w/ chrome rings)/'99 LX - LHS gages (white) - HIR bulbs