If you stacked it on a fire trail, I'd suggest calling the ambulance before
tackling *real* DH trails.
Those skills take thousands of hours to acquire unless you're unusually gifted. Baby steps first.
By the way, Manly Dam is not a beginner's trail despite what the Council's website says. It is Intermediate, blue on the IMBA scale, with some advanced (black) sections. IMBA have just completed an audit and Council's rating will change. Have you actually ridden it? Were you able to ride all the descents without dabbing? If so, I'll take back what I'm thinking.
Edit: OK, maybe I misread the intent of your post.
I ride Manly Dam several times a month, without pads, and it's one of my favourite rides because it's fun and challenging, and gives me a full body workout. Three laps around there (30-odd km) is as good as a workout as 60km round trip out to and around the Terrey HIlls trails, and back. But be warned, any sections you can;t see how to ride you should walk. Mistakes will bite you at the Dam.
If you're still in the skills acquisition phase of your mtb journey, knee and elbow pads can help with confidence, but they are hot to ride in. I wore them for awhile because I used to get nervous about clip-stacking with cleats, but when I got the pads I stopped falling off.
Full-face? Nah, too hot. Fox Flux is a good compromise. Extra coverage but still good ventilation.
Full face would have its use at Red Hill and Oxford Falls, but they are not beginner trails, and body armour is a must there, along with 6" travel forks, flat pedals and shinpads. Burly all-mountain or DH bikes are the weapon of choice. Leave your XC weight-weenie bike at home, it will get bent, as I found out. 24-spoke wheels don't cut it, and that was with me doing a lot of walking.
There are other fun singletrack and fire trail options around if you know where to look, and Terrey Hills fire trails are beginner friendly with great views. If you want to tag along on a group ride some time, let me know.