I have done my PSP couple of years ago. Cant very confidently said it helped however it definetely helped me in strengthening my Planning fundamentals.. The calculations of backward & forward pass along with TF & FF manually test your REAL planning skills. Coming back to its recognition, I guess its more popular in US and many major EPC firms and operators recognise this qualification. Here in UK, i havent seen much of awarness on this. Having said that, I would recommend to go for it for couple of reasons. First its test your skills, and secondly this sometimes may help in screening your CV..
On material, I dont thing i got any soft file. Mostly people orders books from their site for study which you may be get form amazon or ebay. I am sorry i cant be of much help to you here.