I run an EyeFinity + 1 setup (4 Monitors). The way you will need to connect is as follows.
1.) HDMI to HDMI (Just a normal HDMI Cable)
2.) DVI (Dual Link) to HDMI (DVI and HDMI both carry the signal the same way, the only difference is the connectors. You DO NOT need an adapter for this, you simply need a DVI to HDMI cable).
3.) Displayport Adadpter (changes displayport to DVI), and from here another DVI to HDMI cable.
I have seen Displayport to HDMI adapters but have heard of several people having issues with them in EyeFinity. Get one of the adapters said to officially work with EyeFinity like below.http://www.newegg.com/Product/Product.aspx?Item=N82E16814999033
To answer your other question, in Crossfire, you can only use the connections on the primary card. All outputs on the secondary card are disabled.