Welcome to the forums Kerri!
Is this the auto-thyristor type or the new one?
If the old one, just set the flash on "auto" and let the auto-thyristor do its job.
It has some sort of meter/eye in front of the flash that automatically meters the flash output and cuts it off when it gets the right amount of light.
I think those go for $25 or more?
If you want P-TTL then just go for one of these:
DEDICATED AUTO PTTL FLASH FOR PENTAX KM K200D K20D K100 | eBay
..this will provide you with a bit of bounce too and it is P-TTL!
I would say it would be the same size as the AF200S with a couple more features with just adding a couple of bucks.