It will delete evrything from the hard disk and that includes all your private data - documents, music, pictures, contacts etc. Not a good idea. You could work this yourself or take it to a professional PC fixer. The operation is to remove the hard drive and slave it to another PC using a USB caddy.
If you do it, you keep your privacy but some so-called professionals might just keep a copy to sell the bad guys. Using the machine you're posting from, search for the make and model's service manual. That shows you the screws to remove the drive from the inside. You will need a 2.5mm Pozi screwdriver, an old plastic bank card or similar and something small to hold the tiny screws - preferably with a...