80 degrees is too warm. You will not hurt the yeast, but you will get a lot of off flavors. Probably very fruity flavors and maybe buttery flavors. Temperature control during the early part (including the moment you pitch) is one of the most important factors in brewing good beer.
Different yeast strains have different temperature ranges. Luckily you have a yeast with a higher temp tolerance (59-75). You would shoot for the upper end if you wanted more flavors from the yeast (fruity, maybe banana), and the lower end if you wanted a clean beer. A good rule of thumb for most strains of yeast is the mid sixties, but you should look up the temperature range for each strain you are using. Also, after the majority of fermentation is complete, you can let the temperature rise without a problem (in fact it is good practice to make sure the yeast finish the job).
Also somebody please correct me if I'm wrong (I don't work with dry yeast very much), but you don't want to stir it into the wort. Just pour or sprinkle it in.
Lastly, even though the directions say to just sprinkle it in, rehydrating is best for the yeast. This is not necessary, but more yeast will live if you do it. Just make sure to keep everything sanitary.
To rehydrate:
Bring yeast packet to room temp
Boil water for 10 min
Allow to cool to 100 deg (between 95-110)
sprinkle in the yeast
allow to sit for 15 min
stir
let that sit for a minute
stir again
allow to cool to within 15 deg. of your wort
then pitch