I see you were trying to use MoneroX, what were you using before?
If you are using simplewallet it is easy to get the mnemonic seed by typing "seed".
The .bin.keys file is the important one, remember that. The only way to import your wallet to MyMonero online is with the mnemonic seed. You can't just get this by looking at the .bin.keys file because it is encrypted, so open with simplewallet and type seed.
The "transaction too large" error is a problem that to my knowledge is fixed in the current versions of simplewallet. If you are not able to compile the latest version of the wallet from source, try sending to another address with 0 mixin (transfer 0
The reason you are getting transaction too large is that you have a lot of dust outputs.