Security of your property depends on the type of lock you are using. A burglar can easily pick any type of lock with only a key in the knob or handle. This type of lock is marginally secure. Also old door locks can easily be picked out without much hassle.
So its very important to repair or replace old locks for enhanced security. Some locks are of very complex design and only experienced and trained locksmith will do the job. They require special tools, pins or wrenches to repair.
Call any reputed locksmiths for this job or get recommendation from your friend or relative.