for the execution of the volley - watch the 'flow volley' from tomaz that i just posted.
for positioning and timing of split step.... I think the biggest challenge is developing the '6th sense' of anticipation, picking up ques of where the pass is going etc.....
I don't play S&V nowadays.... but my own experience is, if you practice net rushing a lot, either off a serve or an approach, you will develop the sense and just 'know' where to cover.... it's very difficult to cover the entire width of the net (and the lob) just using your reaction off the split step.
playing mostly at baseline - the anticipation skill for volley will suffer from atrophy.