I would say it sounds like reflux too. My son had this. He was on Prevacid until 9 months and then was weaned off it over a one month period. He still spat up until he was about 2 years old, but it was not a daily occurance anymore. Reflux HAS to be treated for 2 reasons. 1. It will burn and damage the esophagus (sp?) and cause more problems later. 2. Left untreated it is not uncommon for a child to have food issues. They associate the pain from the reflux with food and don't want the food for fear of the pain. This is one of the problems my son has. You do not want to deal with this-believe me!
I have not heard of Gentleease. Must be new since my son was a baby. We used Enfamil Nutramigen and the pediatrician told us to add 1 tsp of cereal per ounce of formula. It didn't stop the spit up, but there was an improvement. As far as sleeping, I got a wedge from Babies R Us to put under the sheet. Again, it didn't solve things completely, but it was better. The gas part she will grow out of in a few weeks. It usually improves by 12-16 weeks so you don't have too far to go with that-hopefully. Don't worry too much about forming bad sleep habits if you have to rock her. I spent the first year rocking my little boy. He is now 3 years old and has no problem going off to sleep on his own and sleeps about 12 hours a night. I considered him an awful sleeper (day and night) for the first year and then things suddenly turned around.
Good luck.