1. Go to Microsofts website and follow their instructions, it's highly likely they have instructions in your native tongue aswell.
2. The only difficulties I had after upgrading was I had used a custom location for "my documents" on Win 7, so I had to move some stuff around.
Disclaimer; Nr 2 is highly anecdotal, it's just based on my own experiences, can't guarantee that you will not have any problems - it's a computer after all, so... problems are to be expected