I know this may be an obvious and simple answer, but can mods from FS2004 be used in FSX? I have seen that certain FSX mods will work with FS2004. I figured this meant that FS2004 Aircraft could be used in FSX. If not, can someone please tell me how to convert from FS2004 to FSX, or link me to a tutorial.
Unless stated as you say 2004 aircraft will not work in FSX.
There are so many FSX aircraft I can't see why you need all this conversion work.
Here is a tutorial.