OP here. Looks like we got a much more lively discussion started than I had initially anticipated. I must admit my ignorance regarding professional printing, as I have had no prior experience in the technicalities of it.
The cards in Photoshop *look* amazing, but if they won't turn out well, then that's the bottom line. Unfortunately, I am not familiar with Illustrator, and currently had as my other option Word, which clearly is an inferior choice.
I guess my questions now are two; 1) how can I know if I will get 300dpi at the shop, and 2) will it in fact look good if they can print at that resolution. Firsthand experience is most appreciated - conjectures be damned!! ^^