i've played guitar for what seems like forever and have moved over to bass. my influences lie in metal primarily, but I would like to be able to explore all areas of music, as bass seems to play more of a role almost in some styles (funk, soul etc).

My main question would be that while I was mostly attracted to lead guitar and have an easy time using a pick with bass, I plan to use the finger technique. Do I use just the index and middle, or my third finger also all the time?

any other advise from you bassists would be helpful
Depends what you want to do. Three fingers will be harder to do at first, but in the long run you'll be able to play faster. Two fingers is the norm, and if you don't play songs that require a lot of speed, you'll be fine with 2

Also, you can still use a pick Better to be able to play both ways then only 1 way...some songs require the "attack" of a pick, while others require the warmth and smooth-tone from your fingers.

Learn both
"You have brains in your head,
You have feet in your shoes,
You can steer yourself,
any direction you choose,
You're on your own,
And you know what you know,
And YOU are the one who'll decide where to go."

- Dr. Seuss