You are a newbie! And very ambitious starting out with slackware.
Slackware is not difficult to install as you've found out, but you'll need to do some configuration to get it running the way you want. That's the price of having a fast stable linux system.
Best thing you can do is google up the "Slackware FAQ" and "Slackware Tips & Tricks" The second is by JacK Lai don't know who did the other one.
You'll find most of what you need to get your configuration completed.
Not to toot my own horn but theres also a How To listed under "Other How To's" that I contrbuted to
www.linuxpackages.net which tells how I did some of the things you need/want to do (like getting your sound card module loaded at boot.
The correct run level you want is 4. It is expalined in a text file on your 1st install CD.
There is an ap in slack for configuring lilo> I can't remember the command and I'm not on a slack box right now so I can't check it out.
Check out the three pages I mention above for starters. If you don't understand something, google it.
If you can live without windows for a day or two use your slack boot disk untill you understand what you need to do with lilo.
It's not hard if you don't rush yourself. But your going to learn more than you'll ever learn with an eyecandy default install distro and end up with a very slick system.
Come back here and post if you need more help but you should first try to find the answers yourself and you'll need to understand a bit before you can ask some questions.
Cheers
Rick