If you just want to replace a literal string without worrying about special regex characters you can either
1) use the Pattern.quote(String s):String method
2) wrap your string literal in
'\Q' + someLiteral + '\E'
I think replaceAll('Donotgotothemarketwithoutmoney', 'market', 'TEST') is all you need.
See also https://docs.mendix.com/refguide/string-function-calls
For testing Regex this site is usefull: https://www.regexone.com/
And there you can also learn on how to use regex.