The last paragraph of the Background section should broadly describe the challenges found in the prior art that are addressed by the inventor. The first few paragraphs of the Detailed Description should concisely explain how the inventor solved those challenges.
The Background should explain the problem to be solved, and state that the prior methods were complicated, cumbersome, difficult, or whatever is true. (See MPEP 608.01(c) "Where applicable, the problems involved in the prior art or other information disclosed which are solved by the applicant’s invention should be indicated. See also MPEP §608.01(a), § 608.01(p) and § 707.05(b).") Successful Applicants rarely describe extensive detail about prior art in the Background. A simple statement of the business area and challenges is enough. Background statements generally avoid too much insight into how the inventor solved these challenges.
The Detailed Description should then show the reader how, through insight and experimentation, the inventor solved the problems described in the Background. The Detailed Description can include the questions asked by the inventor that allowed the realization of a solution to the problems facing others. If the invention specifically does not do certain steps, the Detailed Description should list each of the steps that the inventor realized were unnecessary. Any new steps or modifications used to avoid the unnecessary steps should be listed.
As George and Eric have noted, arguments about non-obviousness can be made in response to the Examiner's rejection (if any). The Application need not list all possibly related prior art. It's notoriously difficult to know what the Examiner will choose for making a rejection.
However, the Application should include details that will support arguments of non-obviousness. If the novelty of the invention is that is does not include certain features, the Detailed Description should specifically state the commonplace features that the invention does not include.
A feature in a claim that explains what is not done or not included is called a negative limitation. Negative limitations should be supported by explicit description in the disclosure as originally filed.
I hope this helps. A patent agent or attorney could help answer questions related to your specific situation.