EDIT: Uel beats me, but I wrote a lot so here it is anyway (you can pass the part Uel answered better than me
it asks for the kernel source to recompile it.
It ask for the kernel source because the instaler need it to compile the driver, your kernel wiil be not recompiled.
when I installed VL I didn't choose to install the kernel source so now what?
hmm, I always install the kernel source, so I dont know the exact location of the package on the cd, and I dont know if it is compressed or is already "visible", I dont have the cd rigth now to take a look. Anyway, you can explore the cd to find a package named kernel-src-2.6.xx-xxx-xxx.tlz
If it is no there, you can grab it from the repo here: http://vectorlinux.osuosl.org/veclinux-5.8/kernels/
Be sure you grab the exact version you have installed on your computer (you can find this by typing uname -r on a terminal). If you never changed it should be 18.104.22.168 on the new soho. Once you downloaded the package install it as regular.
And is it safe to do so, and how long does it take to compile?
It is safe, your kernel will be not touched. The time depends on your hard, but is just a moment.
Im running Vector Linux SOHO 5.8 i dont know if theres a difference between the Standard and SOHO kernels.
SOHO and STD have different versions of the kernel. Std have 2.18.xx and soho 22.214.171.124 (I cant remember the subversion of std rigth now and I am not on my computer).