I would first suggest you to visit a periodontist and get your professional cleaning done. After that go to prosthodontist for missing teeth. You can either go for bridges or implants. Implants are usually suggestive in case your alveolar bone is beak but if it is strong enough then bridges will do...
For pain due to wisdom tooth, the first thing to be done is to get the X-ray done...If the wisdom tooth are in allignment than you need to take special care of them and if they are out of arch then it is advised to get them extracted.
Here are few tips to maitain good oral hygiene...It all depends upon your brushing technique...you should atleast brush twice daily. Before brushing floss each tooth properly, than with soft bristles tooth brush gently rub covering tooth and gingiva in to and fro motion. After you are done with all this, to end with you should do mouthwash gargles...for more detailed info on oral hygiene you can read an article given in the link....http://www.identalhub.com/dental-dental-care-for-smokers-772.aspx