Monkey is lethargic and at the vet now

My poor little chinchilla, Monkey... He was fine all along until just yesterday morning. He didn't come out of his hutch in his cage for playtime. Normally he is super eager to get out of his cage so I knew that was odd. Then it was a really hot day in San Francisco (which means it got up to 80), so I was worried it was the heat but I put cool things in his cage and he ignored them. So this morning I took him to the vet. I took him to a vet that will treat chinchillas, thank goodness, but I am worried because what if they don't know what they are doing? The vet said she thought he was middle-aged but he's only 4 years old and I said I thought that was young still but maybe we just have different ideas about age and what am I going to do, quiz her? - what if she doesn't know what she's doing?! Okay, I know, I'm freaking out a little too much. She checked him and seemed like she knew what she was doing. I'm just worried for my little guy. She said with digestive issues, a lot of times chins don't make it, and to prepare myself for that. Of course she also assured me they were going to do everything they could.
They're giving him two broad spectrum antibiotics, fluids, assisted feeding, bloodwork... I'm almost worried that all the things they are going to do are going to scare him to death. How could I leave him with these strange people in a strange place...god I am not handling this well.
Has anyone else ever been in this situation? I could really use some support from people in the community right now. I didn't realize how much I loved Monkey until this happened! He's my baby...
-Amy