Hi pacoandres,
There are lots of posts on the forum for installing a TFT on a Pi. And from the length of the discussions it is not as simple as it would first appear. The solutions tend to require a relatively recent kernel and are mainly aimed at the Pi 2B or 3B. You could try this image, just to see if the "old Pi Rev1.1" has enough umph to proceed further:
#3711 If this works then the following discussions are a good place to start, but this would depend upon the type of your "cheap TFT":
#38591
#47142
Janui