Troubleshooting an IBM 5155 - (portable personal computer)

OK, for a little on topic. Before I go tearing the whole machine apart..... I am the proud new owner of a nice example of the IBM 5155. This thing is in pretty good shape. Turned it on, A: did a quick seek and the I was into BASIC. So far, so good. Now, I'm trying to boot DOS. I have several known good DOS 3.1 boot floppies on 360K disks. I keep an old 486 with a 360K drive just for this (and for creating disks for my Tandy model 4). Anyway, the original A: drive only gives a "boot failure". The B: drive (after a cable swap) boots sometimes. Taking out these drives looks to be a MAJOR undertaking. Not along the lines of multiple years, but they are pretty securly installed. However, I'd like to keep them because they have the IBM faceplate. Now, for the questions... Are these Qume drives subject to any known failure? Should I just dig in, remove these drives and give them a good cleaning and lubricating? I'm used to working with the big 8" drives, where everything is a bit larger. What is the best way to clean the heads? Lint free swab and 90% Isopropyl alchohol? Cleaning disk? Nail file ;-) What's the consensus? Any suggestions or comments in general about this machine? Thanks, Kelly