Basically I'm trying to edit memory (replace branch with a nop so the executable can't branch to auth function). I've done successful reverse engineering on gaming consoles, but I don't really know where to start on PC. WinDbg? VS2010 debugger? I would really appreciate any tips or pointers, thanks :)
I think that what you are looking for is a disassembler for
PE format files (Windows Portable Executable format). The call stack itself has nothing to do with it - you need to modify the flow of a program.
X64dbg are great debugging tools for PC, as well as
Ghidra for static analysis and patching.