First and foremost goto the Hotswapping FAQ
in the tutorials section of this website. There you will find most of your answers.
Second, even before you decide where you are going to put your computer and xbox. Understand that you are going to have open up your computer to disconnect IDE cables and that you have all the neccessary knowledge and equipment. If you have never opened a computer before, this may be something you might not want to do before understanding what is inside a computer.
Now what was said earlier about magnetized equipment, is that any tool that has a magnetic charge within it (many regular tools are... "Computer tools" are not magnetically charged) has the possiblity of ruining computer because magnets displace energy and magnets pull-up metal on boards, disks, and drives. You will serverly hurt your computer and xbox if you use magnetic tools.
Now whats the probability of you NOT messing up? Your probability of how much you will NOT mess up is as good as much as you RESEARCH beforehand on what you need to do. If you are well prepared and have researched you should be fine, unless like stated previously, you use a magnetic tool or you break the pins on the IDE connections, but in my experience of hotswapping, you will get lots of practice when going the route of softmod, because its trial and error.
Last but not least read... I understand that English is not your native language. I would say ask a friend who knows better english and could help translate for you would be a smarter move. Now here's the UDE2 Tutorial
. This will give you the steps. The only difference is that if you are hotswapping you are not going to be using any save files. You are going to use a Hard Drive program such as fatXplorer or HDD_Driver to save or upload each of the files that is required.