You can do Wi-Fi trades as long as you have a Pal Pad. To get a Pal Pad, first you must obtain the first Gym Badge. Afterwards, go to the lower level of the PokeCenter and a lady will give you the Pal Pad. Trade Friend Codes with whomever you wish to trade with, go online, and boom, trade is now ready to go.
I believe Murkrow can be found naturally in Diamond, in the Eterna Forest at night, if I'm not mistaken.