There are lots of good places to buy computer parts. Even though they often give good warranties, the deal off may be that you will pay a little more than you would in other places. Regularly more. Also, due to the sheer quantity of people they see every day, some of the so called specialists don't forever listen to your concern and start jumping to conclusions on what your require or what the problem is.
Some of them take pride that they can give you a technological answer in two seconds and make themselves seem smart, although what they just said is probably wrong. If you walk in and say your computer keeps deafening and he insists you need a new motherboard and CPU to fix it, go somewhere else.