Replace randomly 1000 NA Values in a dataframe column with 0s, without overwriting 1s

I am trying to randomly replace 1000 NA values in a dataframe column with 0s. The column is composed only of NAs and 1s and it looks like this:

  Column
1 NA
2 1    
3 NA    
4 NA    
5 NA    
6 1    
7 NA
...

I want it to look something like this:

  Column
1 0
2 1    
3 NA    
4 0    
5 NA    
6 1    
7 NA
...

The column I am working with has more than 1000 rows, so there will be space for 0s and NAs in the end.

I tried something like this:

is.na(df_col[sample(seq(nrow(is.na(df_col))), 1000), "Column"]) <- 0

This, however, does not work. No NA values are replaced. If I take out the is.na()s it works, but the values 1 might get replaced and I do not want that. Do you know how to solve this?