First of all, I'll refer you to an answer of mine I posted a while back:
The only real difference with the change in handedness is what happens on the Z-axis.
XNA is right handed (positive Z moves out of the screen) and DirectX is left handed (positive Z moves into the screen).
The easy way of converting vertices etc from one system to the other is just to negate the Z value.
Another difference you might notice is that a positive rotation along the Z axis will be different. Easiest way to figure it out: Make 2 thumbs up and point your thumbs towards you. The direction in which your fingers coil around to make a fist on your left hand is a positive rotation in the left handed coordinate system. Right hand, right-handed coordinate system.
If you've got the functions available to you form DirectX, then by all means use them. Test them out, if they work for you, great; if not, observe what's going wrong and feel free to ask another question :)