Partial rollovers are permitted under the tax code. Only the portion not rolled over is subject to tax and penalty.
With 20 years until retirement, don't overlook the time value of your retirement investments. The fact that the money is no longer growing in the pension plan says nothing about investment performance in whatever account to which you might roll over this money. You would usually benefit more from rolling over all of the money unless you desperately need the money now to pay off the debt. Keep in mind that funds in a 401(k) are generally protected from bankruptcy. Even if you choose not to roll all of the money to your current employer's 401(k), you can instead roll that money over to a traditional IRA if you want to have access to that money before you would be able to have access to any money in your current employer's 401(k), even though it would still be taxable and subject to penalty if distributed later from the traditional IRA prior to reaching age 59½.
You might find it even better to roll some or all of the money over to a Roth IRA as a taxable rollover if you can pay the taxes on the rollover using funds from outside of a retirement plan (although perhaps not possible depending on your other financial obligations). If rolled over to a Roth IRA, any earnings obtained in your Roth IRAs would be tax and penalty free once you reach age 59½. Also, 5 years after the beginning of the year in which the distribution from the pension plan is rolled over to a Roth IRA the amount rolled over to the Roth IRA becomes equivalent to Roth contributions basis able to be distributed from the Roth IRA tax and penalty free, avoiding the 10% penalty on that money if you instead took that money now to pay off the debts.
