1) use the sternum to get a good opening cut, b/c you don't risk puncturing the guts. You can slice against it without fear.
2) before I began using a gut hook blade, I'd shove two fingers in that initial hole, and carefully slice between them, pulling the skin away from the inwards, working my way toward the rear. It took a couple of minutes. The gut hook does it in seconds. And the little dull protective tip prevents you from making a stinky incision into stomach or intestines. There's a reason they call them zippers.
3) smaller deer not only eat better (more tender and less gamey taste), they're significantly easier to dress out. The tissue holding the diaphragm and gut bag in place gets thicker and tougher the older the deer gets. If I could, I'd only hunt yearlings. I'd rather harvest two yearlings and field dress and butcher two deer for the same amount of meat, because they dress out and butcher so much easier, and they taste better. My point is, if you can, take a small deer first, if the opportunity allows. Less meat, but easier learning.
If you do, know that those (inner) tenderloins will only be hot dog sized.
4) lastly, if you love venison, great. If you're pallette is relatively inexperienced, learn what makes the meat gamey. If you like it gamey, go kill an old buck. If your wife & 4 children don't, like mine, know that blood, the silver lining, cut of meat and age contribute to the flavor. My favorite cut is the back strap off a yearling or doe. Hind quarters i dice up for various dishes, whereas many butchers will slice this into nice bone-in steaks. But if you're doing it yourself, drain the blood on cold/ice water. It usually takes 2 to 3 days. When the water remains clear (keep changing it out), it's ready to wrap. Other ligaments and fat can cause flavor issues. But I think they can also help preserve the meat better, so learn from trial and error there. If I think I'll keep it frozen for a while, I might let it stay and trim during meal prep. Otherwise, I typically trim it before I wrap and freeze it.