I am going through a divorce and asking for my ex's full 401k since he can't buy me out of the house we owned together. Will I have to pay taxes for that or will he? And how much taxes on 15000 is going to be owed?

The way this works is the court issues a Qualified Domestic Relations Order (QDRO) which dictates that some or all of your husband's 401(k) account is to be split off into a new account in your name. If that is done properly no taxes or penalties are due. This new account may be an IRA that you set up or you may request that a new 401(k) account be established in your name. Whenever you take a distribution you would owe taxes on the amount withdrawn. When valuing the 401(k) account keep in mind that some percentage is going to be paid in income tax, so it's true value to you is perhaps 80% of the account's stated value.

Here's a good summary of the process: http://www.401k.org/401k-and-divorce.php