Hi @milanorwolf
Here's the ifixit Steam Deck repair guide that will help.
It details how to open the console and remove all the parts.
The first thing that you should do when you start is to make sure that you have a clean work bench and are organized having the correct tools to do the work and enough containers etc to place in any components that you remove, especially any screws etc. so as not to lose them
After opening the console, first disconnect the battery as soon as it can be accessed so as to nullify any electrical problems from occurring when working inside the console. Mechanical damage .e. tools slipping etc is another matter so be careful and concentrate on what you're doing.
Wearing a wrist strap connected to an earth point will also minimize any potential for ESD damage to the sensitive electronic components on the board if you happen to accidentally touch them.
To clean off the dust etc, use a soft brush and gently brush it loose and then use a vacuum cleaner (lowest setting) to remove it from the boards etc.
When finished reconnect the battery just before closing the case for the last time.
If you strike problems, stop and think about it first instead of rushing headlong into trying to solve it as you may cause unnecessary damage. This forum is full of questions from users who tore cables, broke plug latches, stripped screws etc most probably due to impatience more than anything else.
Slow and steady and I'm sure that you'll be OK.