Welcome to BF.
you will learn quickly that here you will need a thick skin to deal w/everyones opinions. Do not be offended by the following or anything less than a blatent personal attack.
There are many people who absolutely love anything schwinn, I am not one of them. I think you paid too much for that bike.
Your shifting issues will probably be resolved by replacing the rear deraileur cable and housing and then properly setting it up. Utube is awesome for learning bike mechanics. You can also visit the shimano website, park tools, and sheldonbrown, all will have an amazing amount of good chewy tech babble.
I am not a wheel building guru, when my wheels need trueing I visit my LBS (local bike shop). It is usually about $25 per wheel.
If you were interested in a full restore of your new ride, stripping it down and repainting is an option. I personally would just try to find a touch up paint close enough to the original color and fill them in. If you mean dents, when you say "dings" then ignore this.
use the advanced search option here and search for paint in title only. you will find multiple threads like this one that will guide you through.
I would get this bike in riding order and have some fun. If you decide that you enjoy riding the road, you will want to upgrade. again sorry and welcome.
2010 Kestrel RT900SL, 800k carbon, chorus/record, speedplay, zonda
1997 Trek ZX6000, 6061w/manitou spyder, xt/xtr, time atac