Read these links:

http://www.willegal.net/appleii/appleii-repair.htm

http://www.apple2online.com/web_documents/apple_iie_repair_guide.pdf(pdf download, it is for the IIe, but same rules applies.)

http://www.apple2online.com/web_documents/How%20to%20Repair%20&%20Maintain%20KB.pdf(pdf download for the Apple II)

http://www.toddfun.com/2012/05/28/apple-ii-plus-from-1982-teardown-repair-cleanup-and-demonstration/(with 2 videos)