when starting out with Slackware, the best place to look for initial help is the manual on the Slackware site.
www.slackware.com/book
regarding some of you questions:
1. What apps are you looking for specifically? KDE-specific programs are located in
/opt/kde/bin. you could browse that folder to see if you find anything.
2. do you boot to a graphical login screen or to a console (then typing startx)?
If you boot to a login screen, then you should see something labeled "session", which you click on and select Gnome. then login.
If you boot to a console, then type in (as user)
xwmconfig which will show you a menu of available window managers. Select the one you want, then when back at the command line, then startx per usual.
3. you're right in that each user's "my documents" is located in
/home/user/. if you don't have anything like that , it sounds like you're running X as root (you typically shouldn't be doing that). at a command line, type
adduser and you can create a new user account.
4. see above link.
5. search this site. there's a lot of threads on this topic (perhaps even specific to your hardware).
6. What sort of affirmation are you wanting? Slackware doesn't have a lot of "fluff" that other distributions include. You'll get used to it.
Good luck