th400 questions

can i upgrade to a gear vendors od unit later on if i wish?
does a manual valve body mean i have to manually shift?
is a 350 cheaper? im not putting down serious power, a th350 might be a better choice for me. what are the limits of both? i figure im down to about 360 at the rear now or so...and its gonna stay that way till i can afford to go faster (might be a while now). i need a converter and dont wanna put another in the 4l60e to break it again.
thanks in advance.

