Hello Keven,
Welcome back to the club!
Here's a link to the history section of the official Alfa Romeo website:
http://www.alfaromeo.com/cgi-bin/pbrand.dll/ALFAROMEO_COM/history/history.jspThere's a menu in the right hand side of the page that includes "Alfa Romeo Museum" - click on that and you'll see further links to "How to get here" and "Virtual Tour". I do not believe that you need to book for groups of less than 10, although I would recommend checking that the day you have planned is not a public holiday.
Fi and I went to the Museo in 2002 when we lived in England - we did not make any booking. We drove a rental car and found our way after a few laps of the enormous Fiat/Alfa facility. The Museo Storico is signposted - little weeney red and white signs that are easy to miss from memory. You park in the car park and go visit the security guard cabin - he spoke no english but managed to wangle our passports out of us in exchange for visitor passes. Limited directions so we wandered the halls of the administration buildings for a bit till we found the museum out the back.
The Museum itself is absolutely mind-boggling. We were pretty much alone except for one older man who was measuring the guards on an older car (can't remember what it was) for a restoration project. There was a cleaning lady as well. Amazing selection of jaw-dropping cars - everything I'd ever seen and then as many Alfas that I'd never seen and probably won't see anywhere else.
Excellent stuff - hope you have a great time and take some photos for the Cross+Serpent!!!
P.S. Very interested in the fibre glass body - do you have any photos?