Hi Ronet,
Unfortunately GT can't simply put a tutorial up of a song that is requested here.
Although I think Led Zeppelin and GNR are amazing Guitartricks can't just put up a song tutorial for it. The problem is that even teaching those and other songs (and the TABS for it) are copyrighted. For that Guitartricks needs to work with record companies allowing them to teach some of the songs. Guitartricks, in return, needs to pay for being able to teach those songs legally.
Guitartricks is currently already working with record companies which has resulted in the current lessons in the song section if this site. But my guess would be since GNR and Led Zeppelin are gigantic music names, Guitartricks has to pay a whole lot of money to get those on the site and work with the right record company.
Also for future song-requests I suggest you use the Song-Request forumpage that is specifically for that:
http://www.guitartricks.com/forum/forumdisplay.php?f=58 "
So in short they can't just put a tutorial up because people request. Hope this helps.
JJ