The stethoscope is from when I was in nursing school, I think it's fairly good, so it's not like one of the cheap Walmart ones or anything.
My vet does not like to give guinea pigs injections or at least, take blood. She once told me that in order to get blood work, she'd have to put him under anesthesia and I am not comfortable with that at his age. But maybe an injection of an antibiotic would be different, I could at least ask when we see her on Thursday. I don't want him to get it if he doesn't need it but I'll definitely have his lungs x-rayed. I think he's okay, but I'm watching carefully.