Is it possible to determine what lock cylinder pins are in an existing lock cylinder without disassembling it? I have a complete spare lock set that I want to key the same as my existing key (If that makes sense)....

 

Do you have the keys for the new locks as well? That will help you determine what wafers you have (they're not usually "pins" in an automotive lock, especially in a double-cut.)

Alternatively, simply take an old lock and a new lock apart - there's usually an access cover on one side of the cylinder. Just remove it slowly - the wafers are under spring tension, and you don't want them to get mixed up! If you gently release pressure on the cover, you can lift it off with all of the wafers & springs in place, then pick them out with forceps.

It is possible to source a wafer kit and do the work yourself - but a "wafer kit" is usually going to be designed for a locksmith, and have something like 200-400 parts in it. However, once you've figured out how to do it on your own locks, you can offer to do it for others - it's not terribly difficult, and you can at least pay for the cost of the kit once you get going (I've done plenty of rekeys in the past - I just don't have the materials to do it now. I've considered offering it as a mail-order service, for "project guys" who aren't in a hurry...)