If you withdraw funds, you will pay income tax, no matter your age. If you are under age 55, you will also pay a 10% penalty for early withdrawal. The amount of tax depends on your total income, deductions, filing status, and other factors. There are various income tax calculators on the web.
You have the option of rolling over the money to an IRA. Having the money in an IRA may give you more investment options, but they may have higher cost (higher expenses). The best way to do a rollover is to set up the IRA, then contact the 401k provider and have them do a direct transfer from A to B, so the money does not go through your hands or bank account.
Once you turn 73, you will be required to withdraw a certain amount each year (you are not allowed to leave the money alone forever, you have to start taking it out and paying taxes). But you are certainly free to withdraw the money sooner if you want or need to spend it.
