I agree with wes. If you go to a proshop they should help you with all of that. A few answers though.
1. The draw length "should" be an easy fix at a decent shop
2. If I remember right the xx75's are aluminum. I would switch to some carbons bemans or goldtips possibly. Also decided if you want feathers or vanes.
3. Put an arrow on your string and draw it back have someone mark with a marker about 1/4 inch past the arrow rest. Then measure from the tip (with out a field point or broadhead in) to the inside of the knock.
4. Most on here stick to Muzzy 3 blades their dependable and for starters they are not to expensive.
5. You may want to invest in a release they don't cost too much and for a comound bow it's very helpful.
6. Realize that 40 yards is a longer shot. Most deer are taken closer to 20-30 yards. Before you go out there and start slinging arrows remember your Hunting not Hurting. Practice practice practice.

I hope this advice has been helpful

Good luck and good hunting.