Could you explain me what are diagonal cutters (my english is poor)?
How do they differ from ordinary cutters?
Difference in terminology, most likely. They're often called
'diagonal' or 'dikes' here in the States for the simple reason that the
blades slant at about 30 degrees or so.
Thanks.
What is solder-wick?
Available from most electronic supply stores, it consists of a
small circular package containing fine-mesh copper braid that's been
treated with flux. When held against a solder joint with a hot soldering
iron, it will (usually) have the effect of wicking enough solder out of
the hole for any leads present to be removed without damage to the board
itself.
I'm worried that heat might damage motherboard. For how long should
solder be used?
No more than 20-25 seconds, I would say. Make sure the iron's tip
is clean, and tin it slightly before you go after the joint. You should,
ideally, be working on the board (or any other modern circuit board) on
an anti-static surface.
Good luck.