My husband bought a 2005 E55 AMG last Sat. We've had 8 different messages in the 10 days we've owned it including various bulbs out, check engine, and low coolant temp. They appear/disappear within a day or two, and on the bulb out messages, the bulb is not out, it's actually working just fine. Is this a main electrical problem? Is it a sign of more serious problems to come?

There are a few EPC's online so if one doesn't have the detail or is hard to use try another one. Here is a link to one I have used before to start you out.
http://www.everythingbenz.com/z/epc-mercedes-parts-info-diagrams

there shoild be a pull out panel under the dash pull it out to check the fuses there should be a diagram of the fuse location on the back of the panel

A good engine shouldn't burn more than a quart every 1000 mi. So, 400 mi. is kind of bad as far as engines go. Probably the oil is blowing by the rings and/or there is a seal leak somewhere. The oil has got to go somewhere whether it leaks out or burns in the combustion chamber.

Maybe you could try a high mileage oil that burns off less easily.

about 50 lbs is enopugh and dont forget the grease on the back of the ally wheel and oil on the wheel nut threads

If you don't tighten the gas cap (make it click at least four times) when refueling it will turn the check engin light on. The dip stick is located in the front of the engine and is a yellow loop.

if the alarm have sensitivity setting you might want adjust it

sounds like a major vacuum leak. I would check the hose going to the brake booster(there is a check valve that can fail in that hose as well).

Yes you can.  The bulb number is a "D2S" if you have the HID (High Intensity Discharge) bulbs.  Most auto parts stores will need to order them but it should only take a day or two.  O'Reilly Auto Parts shows the bulb costing 89.99.  They are very expensive compared to the usual $10 bulbs on regular cars. 
If you don't have the HID bulbs, yours is a halogen bulb.  The bulb number is "H755".  This one is the $10 bulb.
Double check which bulb you need before purchasing one! Most parts stores can tell you which bulb you need just by looking at the car's headlights.

Upside Sleek and dignified design inside and out, pleasing blend of ride and handling, powerful V8 engines, sophisticated safety features, all-wheel drive available on both sedans and wagons. Downside More expensive than competitors, confusing control layout, electronically controlled brakes lack progressive feel. What's New for 2007 Most of the changes to the 2007 Mercedes-Benz E-Class relate to engine upgrades. Mercedes' AMG division has renamed last year's E55 AMG as the E63 AMG in light of its more powerful 507-hp V8 engine.

It not happen yet as far *** I know