It is ok for you to translate and publish spanish versions just give proper credit and a link to the article on my site and i make a link from the article to your site.

Doppler is an default effect on openal, i have not written an tutorial on the subject, but there is documentation on the subject in the openal sdk. (should be available on the developer site of creative)

On using directsound with openal have look at lesson13 enumerate devices. But on most soundcards it is the default used.