first of all the network... there is a "network setup" control panel. open the control panel and you will see a "network" option. this asks you the router's internal IP and stuff (usually it's, IP:192.168.1.64-253, subnet:255.255.255.0, gateway:192.168.1.254, dns:192.168.1.254). don't write your IP like that, where everyone can see it (you don't want to get attacked)
second, the installation. since you have already installed OS, you don't need to create another partition for tinycore. it's very simple. just extract the iso somewhere. take the core.gz and vmlinuz files and throw them inside "/boot" (you need to be root to do that). then take the cde folder, throw it inside "/" (as root again) and rename it from cde, to tce (or else it wont find it and you wont be able to install stuff). open the bootloader and add something like this below after ubuntu boot options:...
title TinyCoreE17 Linuks 4.1
uuid 2a626200-e228-493c-af6f-aae4902a886e < replace this with your own drive UID
kernel /boot/vmlinuz root=sda1 tce=sda1 opt=sda1 home=sda1
initrd /boot/tinycore.gz
and finally the stuff you need to install:...
instead of JWM, you can use the elegant DR17 (enlightement WM) with is way more feature-rich.
there is no skype for tinycore. there is only a skype plugin for pidgin. (i haven't tested the plugin to know if it works the same as skype -- pigdin works fine). for audio you need to install alsa from the appbrowser (without alsa you wont have any audio at all)
for this cmus thing, i don't know something to tell you.
the libreoffice suite is available, so you can install it
as a pdf reader, you can use evince or epdfview (epdfview is like "mini-evince")
in appbrowser you can find "firefoxandflash" which i suppose is firefox with readymade flash (i haven't seen it "in action" as i manually download and install flash)
for the php stuff i don't know sonething to tell you.
[ADDED AFTER INITIAL POSTING]
aw... i almost forgot. you also need some filemanager to be able to find and manage your files. there are many of them to choose from. nautilus (very rich-featured but heavy filemanager of gnome), rox-filer (lightweight and very generic xfce filemanager), pcmanfm2 (lightweight fairly-featured filemanager of lxde) and some other, i can't remember right now.
aw, and another thing i forgot to mention. if you have the backup feature enabled (it's enabled by default), don't include the "opt=sda1" and "home=sda1" options in the lines of the bootloader above, as this will "confuse" the system, and you will have trouble saving files and settings.