Goose
Find a couple of spare hours and do a search for "lights" on this site. There is a mass of useful information in there and I found most of it helpful to 1100GS owners despite mainly being 1150GS oriented. You do need some understanding of bike electrics but if you are aware that equipment needs one connection to the live and one to an earthed point somewhere on the bike you are half way there, and if you understand that a relay works by using a low current supply to switch on and off a higher current supply then you know enough. As for tools I would recommend a multimeter for checking continuity (and finding earth points) and a good crimping tool for attaching connectors. You will see much about soldering in connections for the best result rather than using scotchbloc connectors. This is correct, a properly soldered and heatshrink covered connection is the rolls-royce solution. If, like me, you know that your soldering is not above producing dry joints (in the way that the sea is not above the sky) and you don't really intend running through rivers every five minutes then scothblocs and a covering of self amalgamating tape is "probably good enough" (your mileage may vary).
If you are fitting both fogs and spots it is probably worth wiring the fogs via an autoswitch and the spots via a relay into the beam. This means you can run on dipped beam, dipped beam plus fogs, main beam and spots and main beam, spots and fogs (just in case you need to help light up a runway for a jumbo jet to land on).
The Haynes manual for the 1100GS has a coloured wiring diagram which makes life easier - you can use it to track which wires are your feeds.
BTBR has a nice
FAQ on fitting an autoswitch which was most helpful - you can follow that almost exactly to get the main work done.
I did it a couple of months ago - to make it easy I got a fuse box from NippyNorman and stuck that under the seat, then lead the live feeds from that. I didn't do it neatly - look
The big red lead is a feed from the positive pole of the battery, the black goes to an earth point. The fuse box can theoretically carry 60 Amps so I made sure the feed could handle this just in case someone got the bike after me and didn't think. You can do without this, I put it in because I wanted to run a new horn and a couple of auxilliary power connections from it too, just replace it with inline 10A fuses on connections to the battery (Hella lights take 110W each, thats 9 and a bit Amps at 12 Volts). Two feeds, one connected via a relay and the autoswitch wired as per BTBR instructions (although check the wire colour for the switch feed, I can't remeber if it is the same on the 1100 - that's why we have the Haynes manual) and one wired via a relay to a wire (white - I think) in the blocks up front under the tank which carries the main beam power.
I had never done this kind of thing until I decided to attack this job. Take time to read all the advice in the disparate threads and get a feel for what problems there may be. If you really don't want to do it yourself any competent BMW mechanic could probably fit this set in an hour or two of work (although there's probably an hour of bike dismantling and rebuilding to add to that). It took me about a day start to finish but it worked first time.
Mine ended up like this:
PM me if you'd like me to get under the tank and take some pictures of connections or if there's anything you'd like to ask.