might be wise then to phone ahead & explain you are nervous & ask what to expect- once you are aware of what will happen your imagination can have a rest! they are used to people being nervous & are happy (& trained) to help. i think your really not supposed to smoke though so dont do that!
just remember that wether you are calm or stressed that time passes at the same rate. have a sit down & plan what you need like 1 hr getting ready, 30 min travel, 10 min parking & just focus on each thing you are doing.