You can write a function to do both actions.
library(dplyr)
DF <- data.frame(Word = c("piñon", "car", "niña", "bus"), Number = 1:4,
stringsAsFactors = FALSE)
ChgLetter <- function(x) {
x <- stringr::str_replace_all(x, "ñ", "n")
x <- toupper(x)
x
}
DF <- mutate_if(DF, is.character, ChgLetter)
DF
Word Number
1 PINON 1
2 CAR 2
3 NINA 3
4 BUS 4