Hi George,
Information is easy.
The English Vintage Motor Cycle Club has a fantastic Library and it is open to non-members. You can easily get photocopies of anything they hold. I've had a quick look and found they list both a 1954 leaflet and sales catalogue which will give you factory information on what your bike should look like. What colours it was painted, what was chrome plated, etc. I didn't look much further than that but they may possibly have a Riders Handbook as well. You can email the librarian, Annice Collett, at library@vmcc.net for further info.
As the bike uses a Villiers engine you will find it more practical to get original Villiers factory info than rely on Ambassador literature. Annice will assist there also. The VMCC holds a massive amount of Villiers literature covering all aspects of anything thing Villiers.
Further to this your Ambassador is fitted with proprietary Metal Profiles (MP) forks and once again, the VMCC library is about the only place you will get info on MP's. I found this when I rebuilt a set of MP's on my mates 1955 Sun Cyclone.
There are various firms selling Villiers spares. They are fairly easy to get hold of. I use Villiers Services
www.villiersservices.co.uk and have always got everything I've wanted although sometimes service can be a little slow. There are other Villiers related firms but I've never used them.
For easy engine reference probably the most convenient general manual is The Villiers Engine, author B E Browning and published by Pearson. This was published for many years both before and after your 8E came on the market so make sure you have an edition that deals with the 8E. It is often on eBay but I prefer the ABEBooks site
www.abebooks.com where I believe you can get a better quality copy.
Let us know how you get on.
Sorry, last thing. The Guide to Ambassadors book is intended to identify what model you have it isn't intended for maintenance purposes.