Buying a service manual for your cell phone or finding one on the internet can help with taking the phone apart and then being able to put it back together again. Always keep all parts in a safe and secure place as they are very tiny and almost impossible to locate if they fall on the ground.
Many phone repair companies offer either at the business or home service as well as a drop off repair service. If you are sure the problem is in the phone the drop off service can save you the cost of the service call, but if you aren't sure if it is your equipment or the wiring, it may be worth the price of the home visit to confirm where the problem actually is.