Dave- I see from your profile that this is a 1997 rodeo 3.2L. This design has the SOHC's and hydraulic valve lash adjusters. 5Kmi between oil changes is way too much for this engine- regardless of what the owners manual says. At that oil change interval, the small orifices in the lash adjusters will plug will contaminants in the oil, causing the lash adjusters to collapse, which gives the tick noise. As far as the low oil pressure, I have heard of one instance where someone on the edmunds rodeo board had his SOHC 3.2L seize, upon tear-down, they found what looked like gasket material clogging the oil pump pickup screen. He never did give more info than that. I would try an engine flush or two, run nothing but a quality 5w-30 oil at an absolute max of 3000mi oil change intervals. Use anything but a fram oil filter, these have been known to cause low oil pressure issues on startup due to their crappy bypass design. Some "ticking" is normal for these engines & not harmfull unless it's REALLY loud. You'll have to pull your oil pan to gain access to the oil pump & p/u screen if you want to inspect it for clogging.
G/luck
Joel