So this is a bit of an addendum to a question I asked in general before, but I still need some suggestions (my nerves are getting to me) and I have more specific questions now. I've tried searching for the answers, but I can never get more than the first page of search results to load. I can't figure out why.

I'm making a 3-tier cake for my brother's wedding THIS Saturday. I've stacked two tiers before, but not three. I've looked at all the different online tutorials, but I'm trying to find the most "tried and true" method from you guys who do this often (I'm a hobby baker.)

I was going to use the masonite boards I already have and the plastic Wilton dowels. My masonite boards don't have any holes in them yet, so I can't run a dowel through the entire cake would I even need to though if stacking on site? I've read that it's most important when transporting already stacked.

I've also wondered if the Wilton footed plastic plates that are made to fit the dowels would be easier or better. (The cake will be buttercream with fondant decorations.)

If I buy the plastic footed plates that are the exact size as my tiers, they will be plenty sturdy enough to stack, right, as long as I cut the dowels properly? Do I need extra supports other than the 4 "feet" the plate has?

Do I need to put the cakes on cardboard first and then stick the cardboard to the plastic plate, or can I just put the cake directly on the cardboard?

I only have a small car, so no real flat surface stable enough for a tall cake, so I planned to stack on site. I'll be headed to the venue early like 9 a.m. (it's only about 15 minutes from my house) and the ceremony is at 4. I'll have some other tasks to do though, like setting tables and decorating the space.

The design will be similar to http://www.flickr.com/photos/studiocake/4002929091 without the flowers or birds, so can I place most of the little twigs on and add the bottom row after stacking? Should I wait and try to do all the sticks (basically all the decorating) after the cake is stacked?

Any help is GREATLY appreciated.

Well, if you had more time, I would have strongly recommended using SPS. Since you're stuck with Wilton products, here goes:
1. Yes, the cake tier goes on a cardboard circle. You can always assume this.
2. The four Wilton Hidden Pillar legs will be plenty of support, cut to exactly the same height as each other.
3. You should be able to place the legs onto the plate and then put the plate and legs together into the cake tier. If you don't understand what I'm talking about, go on and look at the SPS tutorial. (Directions in my siggy.) One of the many, many advantages to SPS is that the SPS legs lock into the SPS plate. Wilton legs, not so much, so try adding a little bc into the top of the leg to attached the plate.)
4. Completely finish decorating the bottom tier. There's no reason not to and it's one less thing to do onsite.