Well now I can't stop thinking/worrying/stressing about it after reading lots of Kombi stuff on the interwebs...

Van was painted apparently 5-6 years ago and obviously they thought the mod plate wasn't important :/ and yet it has the compliance plate at least.

How important is this Sopru Compliance Mod Plate for my Licensed camper in WA (we don't have annual inspections), does this make the van not worth owning/spending money on?

Why cant I replace the plate and was it illegal to remove?

Should I just be happy and drive it?

The only problem will be if you sell it interstate. But that will not be your problem. Just forget about it as I don't think earlier campers had the plate.

there should be some records at MTD in any state
but wouldn't worry till you sell, if they don't find it it maybe orig from another state?
Do you know previous owner?