How do you know if you really need it and how much training to get? I ask this because I think I already have a naturally feminine voice. I'm a server and on more than one occasion, a customer will slip up and call me ma'am before correcting themselves even though they were right the first time. I'm not trying to sound feminine, I'm just speaking in my natural tone. I still think I need some work to perfect it, I just don't know what to fix and what to keep that's already working.

Besides pitch, you want to have good enunciation of the words, modulation of sentences, and a rising pitch to finish sentences.  It may be possible that you have learned a very feminine voice by emulating women.  I had speech therapy from a women, so I naturally copied the way she modulated her sentences.  Women talk faster with more complicated sentences, which mirrors how I think.

The rising pitch at the end of the sentence is for questions.  Also the pitch is used to place emphasis on specific portions of the thought.

I went to a voice therapist that was based at a major hospital - she primarily worked with people that had physical damage due to disease or trauma but a few years ago she trained how to work with transgender women.

She gave me a bunch of exercises to do primarily related to how to use your breath.  Also an app for measuring Hz of the pitch of your voice.  Another thing she focused on was generating the sound and resonance more from your mouth and less from your chest.

I still suck at it but I am better than I was.  My goal at this point is just to eliminate the deep resonance and at least bring up the pitch somewhat.  I get misgendered often on the phone or fast food drive thru but at least I don't have a bass voice coming out of the face in my profile pic. LOL

A lot of it is your comfort with your voice. If you like your Voice, don't worry about it. Voice training is helpful with identifying what you like and don't like about your voice and the ways to adjust it. How much training is all in how much you practice and how quickly you catch on.