Others have given you good advice, so here is a niche point. Last summer, I bought a Singh-Ray Vari-Neutral Density filter--you can rotate if , which allows you 2 to 8 stops of neutral density. It by far is the best filter/accessory I ever have bought. This winter I have been taking photographs of "seascapes" and urban street scenes (but not street photography). It really allows you to create some amazing photographs. I started with one ND filter that was coated to achieve 4 stops of ND, but being able to increase or decrease the stops with one filter really is the only way to go. It is expensive (around $350 US0, but it is a great tool. I bought the 77mm, which works with 2 of my Canon lenses.
http://www.singh-ray.com/varind.html. I've already gotten way more that $350 of value out the Singh-Ray filter (and I am not talking about sales--I photograph for fun).
I've had the 5D Mark II in Greece in the summer and India (dust and heat even in November). I also did the New York City Annual Halloween parade in the pouring rain using a plastic cover (probably foolish). Never had a weather problem with the 5D.
As an aside, your problem (timing) is one reason I have two regular camera dealers rather than buying all my equipment mail order based on price alone. I suspect that a dealer might find a way to help you out in this pinch with a loaner, cheap rental, or even getting you to the head of a list. That's not to say you don't have a dealer or that you are "bad" if you don't. It is a reminder to everyone that sometimes paying rock bottom is false economy in the long run. Service still counts for something.
Have fun.
Jack Siegel
