W124 Euro lights installation - Advice needed

[Zeus]

So I have my new Bosch Euros and I'm planning my install. I've done some research on this site and others and have read as many of the threads as possible regarding installation. I've learned quite a bit but I also now have some new questions... if anyone could help out, I'd really appreciate it. I want to install this weekend, so any timely advice would be welcome!

1. Relays/wiring. Should I just use the existing system (i.e. keep all factory wiring as is and just switch the multi-pin connectors)?
Or is it a good idea/advisable to install the lights with new, heavier gauge (12ga) wiring such that they receive power directly from the alternator through relays (i.e. run new, heavier wiring from alternator, with fuses, into relays to the lights)?

2. Bulbs. From the posts, I've decided to go with a Xenon H4 bulb, 60/55W. If I were to go to the stronger 100/55W can the existing wiring support this?

3. Vacuum control. I'm going to hook up the vacuum levelling control. Can I just tap into the Economy gauge vacuum without screwing anything up?

I think that's it for now. I'll be documenting the procedure with pics this weekend, and I'll send them in to the site when I'm done. Thanks!