Torn between my new job! Need advice!

So I’ve been working at an animal hospital for 2 weeks now (obviously new) and they just started training me today and yesterday as a receptionist. I am suppose to be an assistant but they want to cross train me. (I also go to school for vet assistant). I really love being an assistant but am having such a hard time with receptionist! Being an assistant they always praise me but up front it 100% feels like a totally different job. I feel like I’m bad at juggling the client in front of me and the phones and I’m not so good at math and it all seems so overwhelming. I’m afraid that I will not improve or worse make a big mistake while up front and piss the owner/vet and other people off. I’m not sure if I should confront the office manager about this but I don’t even know what I would say. I just really don’t want to mess up and the work up there is not work that I am very good at. I also am not a fan of dealing with money because I don’t want to be the reason the drawer is short or anything like that. Any advice?