Welcome aboard the best Z Forum. Expect some work sooner or later, 20 years on gaskets tend to show up as oil leaks they go brittle with age and repeated heat cycles. Usual suspects are Cam Cover, oil filter to engine block gasket and sump pan gasket, all easy to spot and deal with.
Tip: Since we are Worldwide update your User details to show your location and exact year and car model, it assists us answering any questions you post, you may have other members close by who can offer assistance if you need it. Bolster your toolbox with a decent code scanner but be aware early cars will have OBD1 which limits the type of diagnostics you can run. OBD2 will work with Creator 310+ scanners and these won't break the bank.