I haven't actually spun any pure alpaca, only blends. And although I have alpaca fibre in boxes, I've never got around to combing and spinning any of it. So I can't offer any help directly on that. However, if you go onto Ravelry there will be plenty of help. Ask in UK Spinners or Ashford UK Spinners - both very friendly groups where there'll be a few people you know
. If you go on AUKS, elainethehill is likely to pipe up - she's done a fair bit of alpaca, much of it when she hadn't been spinning very long.
As to checking the twist generally, I recently learned how to do this properly! Just letting the last few inches relax to see if they twizzle up into spirals doesn't tell you much about how much twist there is in the single overall, nor whether you will like the end result.
So pull a good arm's length off the bobbin, and bring the far end back to near the bobbin. Stroke the resulting 2-ply to settle it, and then see if you have enough twist. Also, if you like the resulting 2-ply, that's what you're aiming for when you come to ply your singles - a lot of people cut off that segment and keep it with the bobbin or fibre to remind them when they come to ply.