Bash script, ask for user input, to change a directory, sub directorys, and file's mtime atime linux recursively

It could look like this:

#!/bin/bash

# 1. change directory
cd "/mnt/harddrive/BASE/" 

# 2. prompt for name of file or directory
echo -n "file or directory name: "
# ...  and read it
read HANDLE

# 2. b - check if it exists and is readable
if [ ! -r "$HANDLE" ] 
then
    echo "$HANDLE is not readable";
    # if not, exit with an exit code != 0
    exit 2;
fi

# 3. prompt for datetime
echo -n "datetime of file/directory: "
# ... and read it
read TIMESTAMP

# 4. set datetime for HANDLE (file or directory + files) 
find $HANDLE | xargs touch -a -m -t "$TIMESTAMP"

# 5. ask, if the name should be changed
echo -n "change name of file by appending mtime to the name (y/n)?: "
# ... and read it
read YES_NO
if [ "$YES_NO" == "y" ]
then
    # get yyyy-mm-dd of modification time 
    SUFFIX_TS=$(stat -c "%y" $HANDLE  | cut -f 1 -d" ")
    # rename, supposed, the suffix is always .txt
    mv $HANDLE $(basename $HANDLE txt)-$SUFFIX_TS.txt
    # let HANDLE hold the name for further processing
    HANDLE=$HANDLE-$TIMESTAMP.$SUFFIX
fi

# 7. stat to console
stat $HANDLE

This is just partly tested, but should be a start.

To get a an understanding of what is happening here, you should look up the following commands: echo, read, test, cut, touch, find, xargs

Besides you should understand several basic bash concepts, i.e. parameter substitution, command substitution and pipes.