Yeah, that's good to go with the P2M compact, then. You can choose the FSA Gossamer or K-Force, or the Rotor 3D (either Classic or Type S) to work with your current BB. All it would require is pulling off your chainrings from the 105 crank and installing on the P2M spider, bolting the P2M spider to the new crank arms, and installing in your frame. If you're lucky, you may not even need to adjust the FD (but if you do it shouldn't be more than a simple limit screw adjustment in or out - the height ought to be good if you're not changing chainring sizes).

If you buy the P2M with crank, the arms will come pre-installed. All you need to do is bolt on the rings and install on the frame.

Must be one of the benefits of the Type S. The Classic came separate for me (which is good because you have to install the chainrings first - I learned after bolting it all together) and requires torquing up 6 torx bolts to attach the spider to the gossamer crank arm.