If you go the MCX route you would have to do a complete conversion to FSX or later format, since MCX will not usually export FS2004 aircraft with the animations intact. This is not a trivial process. I have a tutorial online:
Use MCX to convert FS9 aircraft to FSX format
www.calclassic.com
Thus the alpha channel approach would probably be much easier if it works.
1. Load the headset texture into DXTBmp (download from the web -
http://www.mwgfx.co.uk/ )
2. Alpha/Send Alpha to Editor (leave DXTBmp running)
3. In Paint, make the texture completely black.
a. Click on small black square in upper right area (Colors) - Color 1 should be black.
b. Choose paint bucket tool in upper left (Tools).
c. Click white image below. - it should turn black.
d. Click Save button or Blue down arrow tab at top left/Save.
e. Back in DXTBmp, Alpha/Refresh Alpha. The upper right square should turn black.
f. File/Save As Extended Bitmap
g. Choose DXT1 as the image type in the drop down box (NOT DXT no alpha).
h. Click Save button.
4. Check in FS (after a restart) that the headset is gone.
Hope this helps,