You have a lot of choices to make before you get so far as a commitment. I did what you did, I went from finance to eventually into a doctoral program for clinical psychology.
Do you have any academic experience with psychology/social sciences? If not, you're unlikely to get into a PhD or PsyD program. Your way in the door might have to be getting a graduate degree in psychology/neurology/counseling psychology - something that would act as a stepping stone. Then you have to decide, do you want to do clinical work with clients/hospitals, or do you want to focus on research (or want to do clinical work but want a PhD).
If you have a bachelor's in psychology, and have good relationships with your old professors and/or your alma matter has a psychology doctoral program, you might be able to jump right into a doctoral program. Otherwise, if you take the longer, more expensive route, you could get a Master's in a related area (as mentioned above), then parlay that into a doctoral program. In this case, start to finish you'd potentially be looking at 7-8 years for a PsyD or 9-10 years for a PhD. The PhD route would be cheaper since you're typically doing research, teaching classes, etc. which tends to fund a lot of your degree. Most of a PsyD would be out of pocket.
As for getting experience to tell you if you'd be into it, assuming you don't want to quit your job, that's a little tougher. Most people at some point get stuck in community mental health for a least a little while, so doing voluteer work at a homeless shelter, or attending AA/NA meetings, doing volunteer homeless outreach - that sort of thing would expose you to the less glamorous aspects of the realm of mental health (a large part of it lacks glamour unless you intend to focus on the bored housewives of reality TV stars). Also, if you were to get a graduate degree in, for example, counseling psychology, that would allow you to get licensed, and licensed therapists qualify for about 80% of the work a PhD or PsyD can do clinically (depends on state licensing), so you might not even need to go to the level of doctorate.
There might be shortcuts or better ways, these are just what I'm actually aware of.