1st, PICTURES! :)
2nd, what i would do when I got this horse is, like you said, join up. I love it. Then I would go through all the ground work to see what all he knows or remembers. Fix any holes if there are any. Then I would see how he would react to a saddle. Then I would practice getting up, getting down over and over to see how he reacted to that. Then start walking around a small pen., build up to trotting, then loping.
I was lied to when I bought a 'green broke' horse so because of that I would start from the very beginning and go up from there just incase.
Hope that helps, as for the neck reining, I have no tips. Sorry
Never forgot the horse that taught you to be fearless (Braveheart RIP) the horse that taught you to stay strong no matter how bumpy the road is (Caesar) and the horse that always had to test gravity by throwing you in the air (Cali)