Career Advancement in the IRS

I’ve been working at the IRS for three years now, and worked two different jobs within the agency. The first job was a seasonal job as a Tax Examining Technician (GS-0592-04) for about 6 months, and the second job is the one I am currently at, Initial Assistance Representative (GS-0303-05). Now that I am full-time, I am looking at further advancement in the agency or with government jobs that share my interests. I have a Business Management degree with an emphasis in International Business, and few odd months as a GS-0303-04 intern from college days.

I have several questions about advancement within and outside the IRS.

1.) How does the job series affect the application process? Does it restrict you to a select few types of jobs, or may you still be considered for different types of job series?

2.) What is more preferred- education or experience? I see that one may be substituted for the other at the introductory levels that I am in.

3.) Given the same resume and information is available to hiring officials for the same job title being announced, how come some of those jobs deem me as eligible, but others do not?

4.) Since I have passed my probationary period, I have read that I can apply non-competitively throughout different agencies for a promotion. Is this correct, and if so, how would I be able to apply for their openings that are not available to the general public?

5.) Many of the jobs I am interested in require 24 hours of accounting. Are there any programs available that pay for this required education?

6.) Is there any additional information about a non-career ladder GS-0303-05, and if it is possible to get promoted to a career ladder position with the same or different job series?

Any additional information regarding finding and preparing for promotions would be useful also! I have checked out some library books on the subject, and thank you for your input.