Ollydbg.
It'll ask you to load it using loaddll.exe. Pick no, and you'll fail. Loaddll.exe just loadlibraryw()'s your skill.dll (in this case), I believe.
Now, depending on what you want to do with skill.dll, there's a handful of choices. Ida can give you a nice pretty disassembly, but you'll need another tool to edit it. HxD and FlexHex come to mind first.
EDIT: After re-reading, you said you got the error when you unload? I think I misinterpreted your problem at first. After making your edits, you need to save it back to the file (right click -> write to executable -> all modifications). Then another window will open up, right click -> save file.
It'll automatically unload upon closing (or when file -> exit/close).