Order new parts?
I've only had to order one new part. Generally, when I make a mistake, I find a way to fix it, using the materials on hand. When I built the tanks, I broke one of the fuel pickup tubes. Apparently, it is not a good idea to try to bend the tubes after you cut the slots near the end of the tubes. Unfortunately, Van doesn't give you any extra for most of the parts, and there was only enough tubing to make two fuel pickups, so that had to be reordered.
Just think of this as an opportunity to buy some of the extra supplies that you think you might need later. Not to fix things so much as to be able to add something special to your kit down the road. Like when you want to add access panels to the rear baggage area. Like I said, not to fix a problem, such as forgetting to bolt the seat belt tie downs prior to riveting on the baggage floor, but rather so you can inspect that area later.
Now, if you want to know how many screw-ups I have made that could have been solved with a new part. Well, I don't keep track of those things, but certainly the number is less than dozens.
Build on,
Tracy.