in the interest of chainline you will more than likely want to replace the bb anyway. so yes, removing it will be necessary. pretty cheap sealed cart bbs can be had in a myriad of lengths. as for the rear wheel, re-dishing an old wheel is fun, but it can be _very_ frustrating, especially if you are "new to this." just a word of caution. i think you would get more props from people who know what they are looking at if you are strolling an old 27" wheel with a aftermarket flipflop hub that you re-dished yourself. just my opinion. everyone can pedal. only the righteous understand.

[EDIT]
yes now that i actually read your post i see you are interested in maintaining the old crankset as well. this may or may not be possible, as i said above, in the interest of chainline (fairly important for fix) and the ultimate dish of your wheel you may well need to upgrade.