You have two different things going on with your 401(k).

When you leave employment, any outstanding loan balance is deemed a distribution. It is subject to regular income tax and an early distribution penalty (if you don't meet any exceptions). It will be reported on a 1099-R, and it didn't have any taxes withheld at the time of distribution. It is no longer a loan, you cannot repay it any further.

If you want to roll your 401(k) over, either into an IRA or another employer's 401(k), then ask the them if they can do the rollover directly to the new trustee. If they can, then there will be no taxes withheld, and a trustee-to-trustee rollover has no tax consequences (though you should receive a 1099-R for it, showing no taxable amount).

If you aren't sure yet where you want to roll it, or if they can't rollover directly to the new trustee, then they will distribute to you and let you get it into the correct account (remember the 60 day limit here -- if you miss it by even a day, the whole thing becomes taxable). If the 401(k) cut a check to you, they are most likely going to withhold 20% for federal taxes. You either have to make up that amount from your own funds, or it will become taxable to you.

An example -- your 401(k) has $100,000 in it. The company sends you a check for $80,000 and says that the other $20,000 is withheld for federal taxes.
You have to deposit $100,000 into an IRA or other 401(k) for this to be a completely tax-free rollover.
If you can't, the tax situation is: you will receive a 1099-R for $80,000, which will show as taxable but you show on the tax return that it wasn't, and another 1099-R for $20,000 which didn't roll so it would be subject to income tax and penalty (if no exceptions apply).

So you might receive as many as three 1099-R's from this, including the one from your loan balance.

Have you got a new position elsewhere? If you do have a new job the best thing to do would be to rollover your 401k. Speak to your new boss or head of finance at your new job and they should be able to advise you how to rollover your 401k.