I did my headlight removal ('94 R100GS) without reading the book so I am going to ignore their suggestions and give you my two bits. I've been in this area several times and this is what I do. You might get away with only pulling the side fairings off and leaving the center faring in place - no Roo bar removal required. Undo the tach cable on the L/H side as that is now right in front of you - be careful because the fitting on the back of the tach is plastic. Undo the knurled hold down nuts for the speedo & tach and remove them completely. You should now be looking at the back of your headlight through the holes formerly occupied by your gauges.
The headlight frame is a two piece affair and is somewhat delicate. The forward part is a frame mounted to the fairing/Roo bar. The headlight bulb is attached to a rear frame which is mounted to the front frame by two delicate adjustment assemblies (one for up/down, another for left/right). These adjustment assemblies break easily (I was in there initially because one of mine was broken and a P/O had bodged a repair). I would not try to split this rear frame from the front frame in situ because you might break it. I would remove the bolts holding the front frame from the fairing/Roo bar and take it out as a complete assembly. All in all, an tedious job and I am a mechanic by trade.
When you have the headlight assembly out on the bench, give the adjustment mechanisms a look over for wear/damage. Now is the time to replace the bits that break - BMW sells them still. Some guys put the springs on the headlight adjustment screws, but I chose to cut them in half before I installed them because I figured they were putting too much strain on the delicate mechanicsms. So far no problems. Just take your time and this can all be done in a few hours. I hope that this isn't too muddled.