Ok so I'm horrible at leveling apparently. This cake looked good,  then I crumb coated and now.....ugh. What do I do?  Rebake? Hubby says try to use frosting and then make sure the next tier is level.  It will be covered in fondant as well. 

NO.....

Set it between two tall cans or boxes, whatever you have one hand (shortening cans, large vegetable cans, etc.) that are pretty much level with the lowest side, then use a long knife balanced on the cans, or a piece of dental floss, and trim the top of a bit, the crumb coat the top again. 

If you build up with icing, it's like to deform under the fondant over time and cause your fondant to wrinkle.

Yes you could do that.  No need to rebake.  If you want, if the difference is drastic, just trim the top off to make it level, and refrost. Use a leveler or a knife, abd be sure to measure from the bottom  

That's the reason I invested in a cake leveler; )

I've seen people who baked their cakes in sheet pans then cut out the desired shapes....i'd never be able to get a level tier that way....but you could stack and fill a bunch of layers then use a good leveler like an Agbay set at 4 inches and level the whole thing at once.

I got my first leveler on eBay for about a buck  with free shipping.  I just won another one today that has two wires for $2.50.  So not exactly a huge investment :) 

there is an agbay on there for $25 I think, but I have been happy with my $1 leveler  

While I am sure that an Agbay would make levelling simpler it is not necessary to get level layers. I do mine when they are still partly frozen.

While they are still partly frozen unwrap them and if you haven't already, measure them and decide what height layers you want to do.

Take a thin long bladed serrated knife and using your ruler mark the cake the whole way round at say 2cm (I either do 4 x 2cm or 3 x 2.75cm). Do all your line marking now so say one line at 2cm and one line at 4cm.

Sit the cake on it's bottom and use your serrated knife to cut through using your 'line markings' as your guide.

By the time your ready to cut your cakes after marking them the should be basically defrosted except for the middle, when 'linemarking' particularly for a round cake I do it while it is still pretty frozen as I tip the cake on it's side and a defrosted round cake will get a bit squished. 

When cutting through the cake keep your hand on top not on the side otherwise when you come through the frozen bit you may find the knife saying a little hello to your hand ;-)

I always have trouble using my big Wilton level (the one with the serrated blade). I always manage to dig into one side more than the other.  What I've found the easiest for me is to wait until the cakes are cooled and the put them back into their size baking pan and simple run a large serrated knife over the top using the top of the pan as a guide. Hope this makes since.

The Agbay (any model) is absolutely your best friend, best cake tool and totally worth the investment.  You'll save time, headaches, worry and cake.