Your friend has a big problem... With the right tools and a little luck, you might get it done in a day if you are a fair mechanic. While the heads are off, it would be a good idea to have them checked for cracks and warpage.
Not a job for an amateur. Being that you have no experience, how do you know it needs a head gasket ?? Tell us some troubles that make you think so. I would bet some "mekanik" told you. Did you run a compression test ? Very unusual to have so many head gasket problems on this forum. Most turn out not to be.