We are spoiled by having some GREAT LFS around the area, they are all nice, knowledgeable, friendly and all around great stores but if you are in to fish, Tuan's store is a must stop.
I agree with him. Is it a steady 82 degrees? Or does it go up and down from 79 to 82? If it's a steady 82 I wouldn't stress to much if everyone is doing fine. Lol I used to worry like that when my tank was fairly new... Now I just try to enjoy it even though is not looking it's best at the moment.
You should be ok using the same sand just give it a quick rinse in old tank water and transfer it, that's what I did when I upgraded from a 60 to a 120. I didn't have any problems.