A'ight, gonna do my best to stick to the questions and not stray too far.
1- You don't really need to be Holy to heal instances until at *least* 50. As long as you carry a few extra pieces of gear with more +Int to fuel your heals, you should be fine. As for tanking, there are some key talents in Prot that really make it easier to keep threat, live longer, etc. I'd still consider Retro for the first levels until 40 or so, at which point it is generally agreed that Prot becomes great for soloing. (Since you can take on 3-6 mobs at the same time solo)
2- Well, it'll depend on the spec you choose. If you decide to remain Holy all the way, I'd suggest mostly +Sta/+Int both to live longer and fuel your abilities. Some +Str may help, but most of your damage should come from magic. (Judging SoR, etc) If you decide to go Retro, +Str/+Agi and some +Sta should do, much like a Warrior. And Prot should be +Sta/+Int as well, with some +Str for good measure. But frankly I think you'll be able to figure it out as you level. If your damage is mostly physical, Str/Agi. If it's mostly magical, Int/Stam.
3- Again, depends on the spec. With Retro you'll be using a two-handed sword. I recommend keeping a sword (mace) and shield for when you need to tank. With Prot it's definitely sword (mace) and shield. And Holy, I think I'd say two-hander until you get to the Outland and can find swords with +SpellDmg, but that's another story.
Not too sure myself what the Sticky contains, but I'm convinced there's a ton of info that could help further.