In the hypershade, with your object selected, you can create a psd network, select the channels you want to work on (e.g. color, bump), check include UVs, then open that file in PS. You can then use the different layers as you like to texture. To refresh your texture in maya, there's a command in the hypershade to reload psd networks (you can make a shelf button).

Just going by memory here, so might be a bit incorrect, someone correct me please. Hope that helps you out. It's not as complicated as you think at first.