YNA's are fun. They can also be VERY loud, but usually when they're demanding something (our CAG asks nicely - our YNA yells loudly!). From my experience, they tend to be one-person birds (not all of course, but many...), and form a powerful, long-lasting bond. It can take awhile to gain a 'Zon's trust. My YNA has been with me almost 2 years, and he's still building trust. No one else can get near him - he's totally bonded to me alone.
The toes issue can, as SailBoat mentioned, be an issue for perching. My 'Zon's feet are normal, but he prefers larger perches...he also hates getting onto my hand, but has no problem with stepping up onto my forearm (when he feels like gracing me with his presence, that is!). It makes sense - it's easier for us to stand on something large than to balance on something narrow, so it probably works for parrots, too.
I had a Lilac-Crowned 'Zon with gout, & major perching issues resulted (more serious, I suspect, than missing a couple of toes). I had to make him a little donut-shaped bed to lie on, as he simply couldn't perch.
10 years old is still young for a YNA - the same age as my YNA - he's more or less an adolescent, at that age. Once he gets comfortable, you'll be seeing the hormonal behavior coming out. That can be a "challenge", but it's cyclic, so you get used to dealing with it.
And, as others have said, learn 'Zon body language!! They're pretty much in-your-face about their mood, and unspeakable evil will befall those who fail to heed it! (Amazons NEVER bluff!! If it looks like he might be looking to bite, he WILL bite...HARD!)
Keep us posted!