JFP's great recommendation is not expensive.
I got my slightly used ,Pyle digital Manometer "PDMM01" for $20.
https://www.amazon.com/Meters-PDMM01-Digital-Manometer-Measure/dp/B005FU5HFI
I bought a new oil filler cap.The old one was used to modify for a 1/8" tube fitting.Search for details/photo.
Hopefully you will seldom use the tool. But when you do, the information is invaluable and easy to read.
Replacing an AOS is a tedious job but if it was unnecessary ..... grr.
If you do catch an AOS failure early, there is less oil to clean out of the intake system.
Let us know how it works out and good luck !