There is REUSE, which can fetch licenses to a LICENSES directory, add SPDX-License-Identifier and copyright notice headers to files, and generate a little dep5 file containing a little bit of metadata. The things it does are documented in a short specification.
No, to use the GPL, you are not required to add the GPL boilerplate to the files. Something like SPDX-License-Identifier is a good idea anyway.
See also the topic here.