That particular module should already live on your system at:
For instance, in the woody kernel, it was here:
You can also verify by checking the kernel config (/boot/config-<kernel-version>) and grepping for I8K.
Using the woody kernel as an example again:
$ cat /boot/config-2.4.18-bf2.4 |grep I8K
You can easily insert and remove modules using the modconf utility.
I don't have a machine here locally that runs the default 2.4 kernel for Sarge to check with for sure, but I'm almost positive it should already have that module compiled in.
shows that it doesnt' seem to be compiled into the default 386 kernel, but perhaps you could install the 686 kernel instead -- it is in there already.