Al
the basic upgrade is 49 §, but if you want all the Real Drums you need the 25-PAK upgrade (you get also a few bonus RD styles, aside from volumes 1-3, with it). If you want to know which styles are within which volume, follow the link Rikki gave earlier in this same thread.
Speaking of Real Drums and Tyros 2, I think that our best option could be synchronize (via midi) the T2 and the PC (using the PC as a master and T2 as a slave, or vice-versa); you could then play the BIAB song (with the Real Drums) from the computer and use the T2 as a sound module, for the remaining style tracks. This would free your left hand from the task of playing only notes that the arranger can recognize to identify the chords and use a more pianistic approach, i.e. comping at will or playing arpeggios, etc.

Just an idea...