My suggestion would be to troubleshoot the problem yourself and buy/replace whatever broken part is in your PC. If you would rather have a professional do it, this site doesn't look like a bad option, but I don't know of many in the first place so I'm probably not the best person to ask.
Seeing as how something burnt in your system, I'm going to go out on a limb and say that your CPU or GPU overheated.
I would love to be able to help but I can't tell what the problem is by what you are saying. I agree with what gizmobrick said, I would suggest you try to fix it yourself.
However, if you aren't good with computers or fear that you may mess something else up, then I would suggest that you have a professional do it. I, personally, suggest going into a local computer or computer supply place and have it fixed there, but that is up to you.
As for whether or not that is a good price depends on the issue. If it is a CPU problem, such as overheating and burning your CPU, or if you overheated your motherboard, or some serious GPU problems then $120 is cheap; however if it is something like a RAM, fan, HDD or another issue with a cheap part then that may be a little expensive.