What is the most efficient way to change character column in a data frame into a numeric column in R? (This would involve changing the entries)

Question

I'm working on some data validation in R. I would like to convert a specific column from a character into a numeric variable. This column contains currency values with a letter and $, and I only want to keep the number part. Due to this, I cannot simply convert this variable to a numeric using as.numeric function. I want to achieve this without changing any other columns in the data frame. Would I just need to split the column into two and just use the numbers part?