Just to help with a few facts (easy to find for those who care). http://worrydream.com/EarlyHistoryOfSmalltalk/

Smalltalk started working in 1972, the Alto in 1973, and Smalltalk on it a month or so after the Alto came alive. The GUI came more from other parts of ARPA than NLS, but there were a few NLS elements. Cheers.