maina,
the only people who can help you renew your diplomatic id is your embassy.
visas cannot be renewed.
you are now practically illegal
if you have been in spain for 4 years, you can apply for residency thru arraigo social or arraigo laboral
use your regular passport in these case. and you have to look for an employer.
do you speak spanish?
mac,
many times diplomats bring with them personal assistants or servants from their countries to their posts abroad.
these people will be carrying service or official passports, because if they carried regular passport, they would be denied visas.