The PLR-22 is suppose to retail at around $300 so expect to pay about $200 for it at your dealer.
As for the SU-22, I have not heard any pricing on that.
From what I hear, the PLR-22 uses many of the same parts as the PLR-16 so expect availability to be easy and plenty.
And YES, the PLR-16 forend will fit on the PLR-22 to give it a mean AR look.
Also the threaded barrel will accept standard AR Flash hiders and breaks.
So instead of the first picture, when you are done with it it can look like my PLR-16.