Flute to oboe.

My band director is letting me go from the flute to the oboe, although he said it will be hard...

Is there any thing I should know before I begin lessons?
What changes to your mouth do you have to make?
Got any good fingering suggestions???

The good news is that fingerings are very similar between flute and oboe.

The embouchure is very different. Oboe embouchure requires quite a bit of pressure on the reed all the way around. The oboe embouchure requires so much pressure that it is difficult to play it for long which is why oboe players are not able to play or practice as long as other instruments. Advanced oboists spend quite a bit of time making reeds though.

Another difference is air. The flute requires a lot of air but has no resistance while the oboe requires very little air but you have to push it out a lot harder. When I learned to play oboe I found that when it was time for a breath that I had to exhale before I could inhale; I never used all my air by the end of the phrase. On flute I usually was out of breath before the end of the phrase and had to try to sneak a little breath.

Speaking of reeds your best bet here is to get your reeds from advanced oboist in your area; handmade reeds are much better than music store reeds. If you are taking lessons your teacher may offer to sell you reeds or may know another oboist who sells them.