Change tranny oil and what kind?

Some trans shops will tell you after 100k that you should not change fluid. I see some valid points in this in that if unit has a large amount of varnish and debris, it could loosen up and migrate to important components. However, I don't entirely "buy into" this simply because in not changing it you absolutely ensure that the unit will fail soon.(the oil itself looses it's ability to do its job, both from a chemical and physical aspect.)
If oil you remove looks burned or is heavily contaminated, change it (with filter) then in about 2000miles, change it again. (when you drop the pan you are only changing half the old fluid, the remainder stays inside the converter) If old fluid is "normal...used" change it once, then again next year (regardless of miles driven).
You can check for exact fluid type by asking at any good trans shop or at a local dealer...its likely dextron 3 but they keep changing requirements. If doing a "short" change use something like the wallmart brand (actually quaker state in a different container) then on second change get and use either the same or better (like a synthetic), adding a good mild additive like the sealer & conditioner made by Lucas. Doing this will not guarantee you will not have a failure but gives you the best protection possible against it.
good luck!