Your employer's 401(k) Plan is governed by the Plan Document, which is a legal document that spells out how the plan will operate and who is able to participate in it. The Summary Plan Description (SPD) is a summary of the Plan Document but is not always 100% accurate and should not be relied on as the absolute last word on whether you can get access to your 401(k) funds via a loan. You should check with your HR department or the service provider for the Plan (ie Fidelity, Vanguard, etc.) and ask if you have access to a loan and if so, what is the procedure for applying. Typically, the service provider will send you an application for a loan which you will need to complete, sign (sometimes a notary is required) and send back. Loans in 401(k) Plans (if available) are restricted to 50% of your vested balance minus any outstanding loans and are capped at $50,000.00.
If loans are not available in your Plan, you might be able to access your funds via a hardship withdrawal. If your need to access your funds is due to one of four qualifying "hardship" expense then you should be able to take a hardship withdrawal. Be aware that a hardship withdrawal will generally be considered a taxable distribution subject to ordinary income taxes. They are usually not assessed the 10% early withdrawal penalty for participants who are under the age of 59 1/2.
In addition to the great advice above, job security is a big factor in deciding to take a 401k loan. If you are terminated or quit your job, you have about 2 months to pay back your loan. If you cannot it will be treated as an early withdrawal and depending on your age you could be hit with a big tax bill and penalty . Unless you have extenuating circumstances, it is usually not a good idea to borrow from your 401K.
Maybe. Every 401(k) is different and is governed by the plan description. Some plans allow loans while others do not. Contact your employers H/R Department, benefits administrator, or the custodian and request a copy of the Summary Plan Description. You can also simply ask them if your plan allows a loan and the forms required.