The first thing I would do is...just shoot the darn thing!
A spring-piston airgun is a sturdy implement of agricultural simplicity, not a delicate surgical instrument. Unless there is an obvious problem, there is no need to douse it in oil before knocking off a few shots.
As noted above, oiling the spring is not really a thing at all. And before you oil the piston, find out whether the gun has a leather or plastic piston seal - you don't use the same lubes for both, and as I noted previously, the 45 used BOTH materials at various times.
If you will post the serial number (on the breech block) and construction date (on the left rear receiver) we can probably research that for you.
Last but not least, I really think you'd enjoy checking out other resources - google is your friend. There are other forums, YouTube videos, dozens of dealers, and other sources of great info out there (for example, googling "airgun transfer port" or "tap-loading airgun" woulda been educational and saved you a couple posts above).