So I'm a novice making a wedding cake for my cousin..wouldn't it figure. My practice cakes went well but the real deal failed! While transporting my 12x12 to its second layer to dirty ice..it cracked! An 8x8 double layer is supposed to set on top of it.. Do I need to remake the middle layer or do you guys think it'll hold?!

I'm not sure I would chance it with someones wedding cake. I would say make it again. Sorry I know that's not what you want to hear.

Make a new cake. I've BTDT before. I thought I could glue the crack back together well enough that it wouldn't make any difference. It did. Once I tried putting in dowels the cake started to fall apart. There is no way it could have supported the top tiers with that crack. So I pulled it apart and rebaked.

When you say it cracked it's very had to tell how bad it is. I have had such problems and have used the cracked layer on the bottom (with the whole layer on top of it) and not had a problem. Another time had the cracked layer so bad it could nto be used so you are going to have to decide how bad the problem is.
You say the only thing going on tip if it is an 8" x8x4" so If you have the cake on a *very firm* base it might be o.k.