Is it better to pay a tax company to fix my i.r.s. problems or can I do this myself?

Havent filed for ten years. possible capitol gaines tax .a 1099 I forgot to file.I contacted a few tax companies and the first one quoted me a price of $5000.00 without even getting any info from me.all the companies I talked to seems to pull costs out of thin air.The most important thing to them is for me to sign'power of attorney paperwork. they all are hounding me for that.