Sadly, I don't think you're sitting on a gold mine.
Musketeers doesn't quite qualify as a "classic" Task Force game (1985 is fairly late in their boardgame production history) and the game was pretty much panned before and after release.
On the positive side, it sounds like you have a nice copy, and condition always counts for something. On the negative side, there is a guy at BoardgameGeek asking $20 for his copy ... and the listing has been up there for 11 months.
Total guess: $10 to $15 if you eBay-ed it today.