Don't bother tearing down your motor. The cost of seals and gaskets is considerably more than a vg30de is worth on the used market.
A JDM NA engine will 95% likely be fine if you change over your oil pan and inspect it before purchase. Do a compression check. if that checks out do the 120k and you'll be fine. (oil pans are almost always dented from sitting on them and this absolutely will cause a serious problem)
Antihero
Putting AMS garbage, and $500 ebay wheels on a Z is like dressing a Victorias Secret model in a Walmart dress and Payless shoes. You're embarrassing yourself.