I think we have all been there and felt like that way back in the beginning. When you get your LR, ask the LFS to fill the 5 gallon buckets your brought with you with water. Then place the LR in those buckets so that you have as little die off as possible on the car ride home. Pending on how much LR you get, your LFS shouldnt charge you for the water.
As far as LEDs go, there is no one stop place to get all the info for your tank. Your tank is differnt than mine. Your inhabitants are differnt than mine. It really is a colaborative process. Read up on what you can and then post questions here.