If you post back, don't use all caps. Basically, turnoff and disconnect the gas/oil line to your furnace. Remove the grate and the screws that is holding it in. Removing furnace without damage to your fingers and toes.
If it is boxed in underneath, you may have to remove the bridging on both sides of a cut off joist to add a 2by extension joist that overlaps a couple feet on both ends. You will need 2by nailers around the inside perimeter for nailing in the new floor.
The tricky part is matching up the floor especially if you want to find hardwood flooring to match. Any thing you do get won't be the same thickness and you may need to use layers of different thicknesses of flooring layered with layers of roofing felt (as a shim) to get the floor even.
I've seen some floors have 3 layers of subflooring and flooring. The new stuff doesn't come as thick as it used to, especially in floor furnace days. Like Wick and Jim are saying, it is hard to get very specific without seeing it. Good luck.