Since a vector file's filesize is somewhat independent of the file's dimensions, it is always best to create the file "at-size" If the image needs to be 30inches by 30inches, create the file at that size. Don't create it at 3 x 3 inches and ask for it to be scaled up. You're just inviting more problems that way. An intelligent prepress guy can get the scaling correct very easily... but many, many, many people in printing are far from this (I know from experience) Don't get me wrong, plenty of smart guys, too, but if you can correct a potential problem from the start that's best.
So. what I would suggest is that you scale the file up (or down) to the correct size yourself & change the document size as well. Look at the detail. If it looks fine, then you are cool. If it doesn't, just post any issues you find here, and I will make suggestions on how to correct them (potential problems include stroke weight & mitering changes, accidentally locked layers, etc)
When this goes out for printing, there are THOUSANDS of methods & pieces of equipment they could use to process your file, so it's best to lessen the amount of work / changes they will need to make to accomplish your needs.
If you are having too much trouble changing the size yourself, then your printer might have better luck, but it's worth giving it a try yourself first.