awk script to anonymize csv file

Job ID: 33818576

Budget: €8 – €30 EUR

I need a awk command/script to anonymize a csv file.
The first line with the header should be kept untouched. For the rest of the file
1) all numbers should be replaced by a random number.
2) all lowercase letters by a random lowercase letter.
3) all uppercase letters by a random uppercase letter.

All characters should be replaced with a random character, but consistently within the run/document.
For example, a random replacement table could be used by each run, which is then applied to the entire document.

If possible (optional) i want to be able to provide text-strings that are exempt from the replacement.
For example if there are email adresses within the csv file I only want to randomize the username but keep the domainname intact.