Devinshire has covered it with great info.
I would add that vets fees for drawing the blood and sending it overnight to the Kansas lab can vary widely -- I think mine were less than $200; if I'm not mistaken they might have been as low as $72 including blood draw and shipping to Kansas taken care of by my vet clinic.
Also, if I were you, I would let the vet take care of getting it overnighted to Kansas for you. Have him or her also fill out a form called the "FAVN" titer test form. This form with info about your cat, complete with microchip number, will be sent to Kansas with the sample. It will also be the one that is sent back by Kansas with the sticker that has written on it the results.
I think the blood sample has to be packaged in a "cooler" type of container, a little like donor kidneys being couriered, so I would rather trust the vet to take care of the shipping to Kansas rather than try to send the sample myself, even though your vet will of course charge you for the FedExing etc.