Personally, I could not complain online shopping, but I had some inconveniences like no answers on my questions, or no wish to explain or to understand my dificulties with goods I bought. It's important. I'm not expert specially in this electronic things, so it's clear that I can do not nderstand something.
And now, finally I'm ready for cleaning and changing pieces:
1/ compressed air to clean dust inside the case I bought in a hard goods shop,
2/ laser lens cleaner I bought in a Commercial Center,
3/ Hard disc and DVD-writer are from online shop.
This evening I'll read the instructions and maybe tomorrow will be dedicated to all these great changes.
Wish me patience and luck in this adventure.
First step: To change a hard disc