How to spoof is just a google away. There are so many ways that I think it's not a good idea to ask how. It's just something that is done by scammers.

As to your account, if you can log in and don't see changes it's very unlikely it's been compromised.

That all said, the current email system is decades old and will for maybe more decades be subject to spoofing. This could really upset folk that didn't know this.