Medically, they are safe to be taken together, however discuss the risks of taking oxycodone with your doctor. Like all opiates, it is addictiive, but used as directed to relieve pain for a few days...
No. You're never supposed to take mental medication for life. You take them so you can live normally and go to therapy. Taking pills without going to therapy is a waste of time.
Generally two weeks for any effect, and up to six weeks for maximal effect. Note that all individuals are highly variable in their response to drugs (especially drugs of this type) so results will...