It just takes practice and experience with Wyrds models to get into the flow of things. You're not alone, my first few Malifaux models looked like TRASH with all the globs of glue where I kept trying to reposition shit or couldn't keep a piece to stick right. I learned over time that it was definitely me not taking my time, focusing, using the right glue, etc... now they're my favorite to assemble.
As far as replacements, keep an eye on Ebay. You can find singles or dirt cheap crews on there frequently.
I usually try to assemble based on the box pictures alone and will only look up the diagram if I am truly stumped. Don't get me wrong they have some SERIOUSLY advanced models in their lineup but as long as the actual parts match up correctly (*cough* The Wild Ones) you'd be shocked how well they sit in place. They're some of the best minis out there.