just add the module names to /etc/modules with any old editor (pico, vi, etc), one on each line. for your situation:
#-----------example /etc/modules-------------
usbcore
usb-ohci
hid
usbmouse
#------------end example-----------
that will cause them to load on boot. as far as wheels go, you need to get your 4th and 5th buttons set up (thats what the wheel is considered, 2 more buttons, one for up and one for down).
mouse section in XFree86Config (or XFree86Config-4) should look something like this:
Section "InputDevice"
Identifier "Configured Mouse"
Driver "mouse"
Option "CorePointer"
Option "Device" "/dev/input/mice"
Option "Protocol" "ImPS/2"
Option "ZAxisMapping" "4 5"
EndSection
that ZAxisMapping part is what does it. if you have a more exotic mouse with 4 or 5 buttons, AND a wheel. the "4 5" might need to be "5 6" or "6 7" or whatever, i've never had anything more than a 2button+wheel mouse myself.