Do not feel too bad
I bought my K0 in 2001 from a motorcycle shop in Farmington NM. The owner told me that they had serviced the bike with new points plate, oil/filter change, new tyres. A price was negotiated at $700 as they had not done the carbs($800 with carbs overhauled). As it was coming back to Sydney Australia, I knew it was going to be a while before I saw it and I decided I would do the carbs when it arrived.
They were honest and had done all of what they said, but I decided to change the oil anyway to be sure and of course, as most of us do, changed the filter as well .
As you have probably guessed ,they had left the spring out, but it was new oil and filter!!!!
How prices have changed in such a short time!!!!!