Diapering and toilet accidents

Hello!I just started as a health room assistant at an elementary school. I have been assigned to special education pre-k to kindergarten students. Therefore I'm the one who needs to do the dirty and stinky task of changing poopy pull-ups and underwear. The problem is that I am not experienced in this task as I don't have a whole lot of experience with kids. Although I am looking forward to advancing in my career as a nurse no matter what I have to deal with. Another issue is that the restroom where the kids are changed do not have a changing table, as they change them standing up to help promote self confidence I guess. This does sound strange but how am I supposed to do this when they are standing? It seems really messy and unpleasant, but it has to be done I guess. Anybody else ever had to deal with this?