That's not a lot to pay for a printer that big.
Getting the frame in square and getting it to stay that way can be a challenge. I ultimately resorted to a mix of the cast aluminum inside corner braces and the plate aluminum outside corner braces, on my 330mm x5s. Make sure you order extras of the inside braces if you buy them, because some of them won't be square. I personally don't think printed braces are worth the plastic they're made of.
The bottom wheel on the carriage tends to get loose and this will wreck your print quality. There are various ways to solve that problem. Easiest is a longer screw and a zip tie.
Make sure you rebuild the hotend. It's usually not assembled correctly at the factory and sometimes there is a burr at the end of the throat.