The 500 is a fine shotgun. Todays 20ga ammo, both shot and slugs, are way better then years gone by. My son took his first deer with this very gun. I have since sold my 12ga and bought a 20ga slug gun. If I haven't replied too late and you're still pondering the question, go buy it. You won't be sorry. Do yourself the favor and buy the combo with the cantalever scope mount. You'll be glad you did.
Try to put your tree stand in a tree with plenty of background cover, keep the prevailing winds for that time of the year to your face, and take care of those pesky squeaks and creaks your stand may have developed while sitting in the shed. A good treestand lube can be made by heating petroleum jelly until it reaches a liquid form. Some hunters have reported success by including a cover scent in this mixture before applying it to their stands.