So sorry to hear about your unpleasant experience at the yarn shop. Let's just hope they were having a bad day. (If not, you need to find a new yarn shop.)
Anyway... on to your question. Yes, for seed stitch on a circular needle (I'm assuming you're working in the round) you would K1, P1 on the first row and then P1, K1 on the next row and repeat. It needs to be over an even number of stitches when working in the round or the pattern will be wonky at the start/end of the round. Whether you are working on straight needles or circulars, with an even number of stitches or odd (which you can do when working flat) the only thing you really need to remember is that every row alternates knit and purl stitches and you always knit the purl stitches and purl the knit stitches (as they are presented to you as you work them) of the previous row.
I hope I didn't over-complicate that! I have a tendency to elaborate way more than necessary sometimes.
Anyway... on to your question. Yes, for seed stitch on a circular needle (I'm assuming you're working in the round) you would K1, P1 on the first row and then P1, K1 on the next row and repeat. It needs to be over an even number of stitches when working in the round or the pattern will be wonky at the start/end of the round. Whether you are working on straight needles or circulars, with an even number of stitches or odd (which you can do when working flat) the only thing you really need to remember is that every row alternates knit and purl stitches and you always knit the purl stitches and purl the knit stitches (as they are presented to you as you work them) of the previous row.
I hope I didn't over-complicate that! I have a tendency to elaborate way more than necessary sometimes.