Hi muddobber
the only HUD option I know is where the front view without the cockpit is shown and it has 5 transparent gauges displayed. There is also text displayed in the top right corner of the screen.
You can delete these gauges or maybe even change them for different ones but I haven't tried to do this.

As far as "fixes" go , getting the 3.1 and 3.1a patches from MS are a must! These fix a lot of the issues.

Then there are lots of scerney add ons , missions etc just look on this site for them.
If you are keen to have a go at changing the Flight Models then I would suggest you get the 1% Flight Models from AV History and load these into your game.
I have tried some of these and they are great-- much better than the stock ones.

I have three installations of CFS3 on my pc as I have three payware products.
These are Just Flights Battle of Britain--great stuff,  Firepower and D-Day.
All of these add- ons modify the original installation and there are some issues with trying to run them all on the same game install.

Also last but not least is the fantastic add on of "Over Flanders Fields"(freeware but a donation would be a nice gesture !) and the yet to be released "MAW" over at AV History.

So get surfin' and find the goodies !!

cheers
chuck