How much am I penalized for early 401k withdrawal? For example: on $10,000 withdrawal, what would the penalties be?

The penalty is $1000 (10%). However, in addition to the penalty, the amount of the withdrawal is added to your taxable income. So you have to pay taxes at your current rate on that money. If you are in the 15% bracket, that would be an additional $1500 you would owe on it.

Taking an in service withdrawal is an extreme last resort. See if your plan will allow you to take a loan out against the balance.