I'm buying a laptop with a Spanish keyboard. Can I convert it to an English keyboard manually, by replacing the Spanish keys?
Yes, you can replace the physical keyboard and change the keyboard language settings in OS to english. I recommend not removing keys one by one, but changing the whole keyboard instead. This might void your guarantee though.
The procedure is easy, I replaced my first laptop keyboard in my life successfully with the help of random youtube video. So you can do it yourself too.