I took the 14mm nut & 3 allen head screws off both sides and can't get the arm off? Is their a trick?

I don't know, as I've never tried to remove mine. The Shop manual might give you some clues. If you don't have it you can down load it from here:

www.tocmanufacturing.com

I don't have a manual & couldn't find anything on that site.

You should not remove the nut as this is for adjustment purposes only. Remove the 3 allen head screws on each side, the adjuster assemblies will then just lift away. You will then notice a threaded hole in each pivot pin (which are now exposed). Screw in a long M5 bolt half a dozen turns then pull on the bolt with a pair of vise grips or similar - the pivot pins should slide out fairly easily (if they don't then you will need a slide hammer). Once both pins are out pull the swingarm back to allow the front of the driveshaft to disengage then you can lift the whole assembly free. Make a note of which sides the adjusters/pins are fitted or you will risk putting the swingarm off-center when you replace it. It is a wise move to pry out the oil seals & remove the bearings for re-greasing while you have it all apart. Also, you may be aware of the problems some of us have had with the sliding joint on the driveshaft - grease this up while you have it all apart - VERY important (I found out the expensive way).

For the online manual go to http://www.tocmanufacturing.com/Products.htm and scroll down to the bottom to
Other Links:

Link to VN700/750 Service Manual in PDF formatt (WARNING 117MEG file) click here

right click on the "here" and do a "save as"