You could learn the basics of manual flash in that time frame, but that is a tough situation to try to use it.
The Metz 36 AF-5 is a bare bones P-TTL flash, it has automated exposure but not much else. It is lacking on power as well, so if you are intending to bounce off the ceiling it might be a little weak. The lack of swivel can be annoying for bouncing as well. It is one of the better P-TTL options in the price range though.
This site has pretty much everything you need to know about selecting a P-TTL flash.
The Definitive Guide - Pentax P-TTL Flash Comparison
There is a middle option, between fully manual and P-TTL. Before TTL flash metering there were "auto thyristor" flashes, they had their own light sensor and you just need to set your aperture and ISO appropriately and they take care of the flash exposure. There are a huge variety of these on the used market, though not all are safe for use on modern cameras. One that is safe and a good value for money is the Pentax AF280T.