I plan on making some videos on this once I get through web vulns. I've written x64 on Windows and Linux. On Windows you need to get ml64.exe, it gets installed with visual studio. You can invoke it from the command line. On Linux I usually use NASM I think, cause it supports Intel syntax.

The only really annoying thing is the stack alignment for calls. I usually just make a macro to check rsp and align if needed. Other than that I think it is similar enough to x86 just with different registers.