Hi Woody and welcome to the Forums! Salvia should do really well in a greenhouse. The 2 biggest things to watch out for are temperature and direct sunlight. If you are in a greenhouse then I am assuming your greenhouse filters the light through the plastic covering which will be good. Temps are ideal between 65F and 70F as Salvia like a bit cooler temperature. However it will do OK in 80-85F temps. Once you get above 90 it starts to suffer. So if your greenhouse is completely enclosed you may need some exhaust fans.
The other big things to watch out for is to make sure you get a true Salvia divinorum plant from eBay. There are a lot of scammers out there, but if you post a picture here we can tell you right away if you got the real thing. Also you may need to cover your plants with a clean cut off two liter for a little while to help keep humidity up to help your new plants adapt. Keep it on about a week then slowly take it off more and more over the second week.
Here is a guide I wrote to help you identify if you got the real thing once it arrives. You are doing good already by getting prepped with information BEFORE the plants arrive. They will thank you for that!
http://www.salviasource.org/forum/pestsproblems/how-to-tell-if-you-have-an-authentic-salvia-divinorum-plant/0/JARG