First of all, I'll refer you to an answer of mine I posted a while back:
Why / how does XNA's right-handed coordinate system effect anything if you can specify near/far Z values?
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 can be left handed (positive Z moves into the screen) or right handed, as pointed out by mh01. Refer to his answer to make use of the right handed functionality of DX.
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 :)