If part of the key is protruding out of the lock, you can use a pair of needle-nosed pliers or tweezers to gently turn the key in the lock to open the door. If the key is fully inserted into the lock, you may also be able to use a key extractor to help turn the key into the unlocked position. 

But if the key breaks off halfway into the lock or you simply can’t reach it to help engage the unlocking mechanisms, you should probably call a professional.

Rekeying is typically cheaper than replacing locks. Professional rekeying costs between $40 and $160, sometimes with an additional fee of $15 to $40 per lock. A locksmith's hourly rate averages around $75. If you do it yourself, a rekeying kit can cost as little as $10. In contrast, replacing a lock costs between $130 and $500, with an average of around $315, depending on the hardware and lock type. Rekeying is a simpler process that changes the key for your existing lock without replacing the hardware. It is a good option if you have a quality lock that works well, you've recently moved, you've lost a key, or you need a quick security upgrade. The best choice depends on the condition of your current locks.

Lock bumping is a technique locksmiths use to quickly and quietly open a pin tumbler lock, typically found in most types of deadbolts. It involves inserting a specially crafted key, or bump key, into the lock and tapping or "bumping" it with a mallet or similar tool. The force applied causes the lock's pins to jump momentarily, allowing the lock to be turned and opened. Unfortunately, thieves also use this technique to break into homes. Luckily, products like a deadbolt strap will fortify your lock.

Typically, it can take around 15 minutes to rekey a lock. The time depends on the type of lock and how skilled you are at rekeying. The first time you rekey a lock, it may take a little longer. Once you get the hang of the process, it will move along much more quickly.