ISO: WEDDING CAKE Mini-disaster .... HELP!

Hello All! I am in need of help! I am a Bride to be, getting married in October of 2008. My dear friend who is a genius with cakes and has her own small business out of her home, I fear, feels to overwhelmed by my wishes for my wedding cake and now will not do it. I am a senior in college with my final semester and a major internship and have no time to work on finding another cake decorator, as all the local bakeries only do white on white cakes that look like they are out of the 1980's and fit the budget that was originally set.

Sooo... I am doing the unthinkable but feel I can really manage the task IF I organize and do trial runs as I do have a few volunteers who are SO sure we can do this (I find my confidence in them). My wedding is very elegant and has a theme of decadence (sort of a soft and organic, toned down Marie Antoinette theme) I would like to do a minimum of a 3 layer cake of like a 16" base 12" middle and 8" top. I would really prefer to do a chocolate cake (I like yellow as an option as well) with mousee/raspberries/ peanut butter or a combo of them (really do not prefer coffee flavored cake elements) and a cream/ivory colored (probably buttercream) icing so that it still fits the color scheme...

I have never done a wedding cake, but I am pretty savvy in the kitchen and always bake for events and things...just never a tiered cake. Are these cake elements too heavy for a tiered cake? Does anyone have any recipes that would fit this size cake including the desired elements??? Any tips or how to "simplify" this process??? And what the heck is crumb icing and how do I make it? lol

Any help or guidance is SOOOOO greatfully appreciated! Thank you with all my heart!!!!!!