Installation can take as little as one day. Please use the following URL for installation guise (look for part one - there are about 6 which cover every bit of installation including some of the pitfalls when it comes to prerequisites):
http://how1think.blogspot.com/search?updated-max=2010-03-15T15%3A34%3A00-05%3A00&max-results=7#uds-search-resultsOnce you have it installed, you go through the following process:
1) Download the msi/exe or extract the media contents to a source file on your server.
2) In SCCM you create a new package and point it to the folder for the previous media.
3) Create a program in the package which is basically the name of the executable and any other switches you want such as /quiet /norestart for invisible install and no restarts at the end.
4) Advertise the program to a collection of computers.
I can honestly say that I had it up and running and installing applications well within a delay using the above tutorial URL I have specified. you can choose to install at login, restart or straight away.
This is a brief run down of the process. It takes a few attempts to get used to all the options (most of which you don't need right away). Also there is a lot of other things you can do with SCCM once you're used to it. I've been playing with it for a few months now and I have to say it's a fantastic bit of kit for managing educational networks (as I'm doing right now)
As for WinINSTALL LE I've never used it but I would doubt it's as comprehensive as SCCM.
Let me know if you have any more questions.