Hi guys, Ive got a question regarding postage

I have zero experience of postage (sending), so I need a few pointers. I wanted to make a postage of a motherboard (which is inside its box). So the following are my questions:

1) Do I have to find another brown box to put the motherboard inside the brown box?

2) How should I properly wrap the item?

3) What postage should I choose?

4) When I go to the post office, what do I ask for? Do I have to weight it first or what?

5) Should there be any damage or the item lost during the postage, me(the seller) or the buyer should be responsible?

Hope u guys can answer my question, thanks