It should not take long time. Specially not if you have bought a banned site. I had sites reicluded in less than a month.
Wouldn't google sitemaps tell you this kind of thing? A total ban is easy enough to figure out: means the pages aren't indexed. Just search for something you know is on your site and nowhere else. If your page doesn't come up - when it would have before - it's banned.
Easiest way to see if your site is banned (kh7, you would have seen it if you bothered to read the thread): Do a search "site:yourdomain.com" in Google , if you get results, you are not banned. If you get no results, you are banned. Don`t make it complicated by searching stuff from your page or what ever.
after doing all your suggestions, i'm happy to know my site isn't banned. probably just lost some rankings.
Google can penalize or ban individual pages or entire web sites. Their decision is based on the type and extent of the infraction. If the infraction does not seem egregious Google will place a warning or explanation in the domain's Webmaster Tools account. However, if the Spam Team at Google (Matt Cutt's team) feels that a domain is purposely spamming with intention they will not place a message in Webmaster Tools. You can learn more about this on Matt Cutt's blog. He writes quite extensively about it.