If I bought a wireless keyboard could I plug it into my laptop?

My sister got a new latop from the goverment so she's given her old one to me, the one I'm using now is almost 4 years old and whilst it sill works perfectly the fact is its spec is terrible compared to modern computers.

But I'm not getting rid of it.

I was to clear everything out of it and use it as a media centre hooked up to my tv but I'll be sat on the sofa and its going to be a pain in the arse getting up and clicking every single time I want to change videos or song so if I got a wireless keyboard would it work?

I was also wondering if theres such thing as a sound cable that connects from a headphone jack on the computer, to a red, white, yellow on a computer and whats that called?

thanks