you can decline a blood test for HIV / syphillis as Helenia says, but you should have one at some point in your life just to check.
the swabs, for me, were ok... very uncomfortable situation, but the actual swabs dont really hurt that much. again, as Helenia says... not at all dignified lol, there is no way you can look cool haha. there is one though, and i'm sorry to have to say this, will put you RIGHT off, but they do one swab of the urethra and for me that hurt like ****. It was the most painful thing ever. Some peopl are absoltuely fine with it, but god dammit it hurt for me. I wish someone would have warned me before i went!!!!
And yes, they ask you lots of questions, how many people in the last year? ho many in the last 6 months? how many unprotected times etc. what protection... usual stuff. Oh, and have you taken any medication or smoked , or taken any drugs.