Hello Sutton;
You seem to be getting quite adept at programming PLCs. Hope you like Siemens' PLCs as well.
First, I don't believe you can download a version of Step 7 (programming software for S7-300 and S7-400 PLCs)from the net; but your local Siemens rep should be able to copy or lend you a CD. Without a license authorisation, the Step 7 software will run in Demo mode, allowing you to try programming blocks and configuring hardware and networks (this is true from version 5.0). You will get nag messages aboout the license, and you will be barred from downlaoding and monitoring a real PLC, but it should give you enough play time to get a feel for the programming environment.
Installation from the CD will place a number of pdf programming manuals on your hard disk. Alternatively, you can go to the Siemens support webpage, do a search on Step 7 and download quite a few manuals for free; the problem is filtering so you get what you need to start. I suggest the manuals "Working with Step 7" and Programming with Step 7"; togeteher they cover most of the functionnalities of S7 programms. The web page can be found at:
http://www4.ad.siemens.de/csinfo/livelink.exe?func=cslib.csinfo2&siteid=cs&lang=en
Finally, the basic difference between the programming style of Siemens PLCs and most other manufacturers lies in the underlying philosophy they have chosen. Most PLCs programs are linear, one ladder file (with interrupts and sub-routines for flexibility); Siemens has chosen a structured apprach, close to the structure of a C program. Machine functions or sections are divided into logical blocks, programmed in seperate Functions (FCs) or Function Blocks (FBs). These can be parametrized individually, and called conditionnally from a main()-type block called OB1. This can look confusing at first, but it can give the programmer great flexibility and smaller, more efficient programs.
Hope this helps,
Daniel Chartier