I see that the USS Shangri La went was the first to be refitted in 1955, and the USS Oriskany the last refit to be completed after a two year overhaul in 1959. Obviously, all 14 carriers would not be out of commission at the same time.
How many months did the average switch from straight deck to angled deck take, and could it have been done during a ship's normal scheduled maintenance time while not deployed?
I would assume it was phased so that one ship would be 75% done while another was around 25% done, was this the case?
Did any foreign powers (e.g. the Soviets or Chinese )make significant moves due to the fact that the U.S. Navy was in this transitional period?
The angled flight deck was invented in a study by the Royal Navy in 1944-45.
The first experiments with angled flight decks were on HMS Triumph and USS Midway. In 1952 USS Antietam had an angled deck installed and US and British forces conducted training on her. The US navy then installed the decks on the Essex class and Midway class carriers as part of upgrade programs during the 1950s.
In 1955, HMS Ark Royal was the first carrier to be constructed and launched with an angled flight deck. In the same year the HMAS Melbourne and the USS Forrestal were built with angled flight decks.
12 of the US Navy's 22 Essex class carriers were upgraded to angled flight decks, (plus the Antietam, with her experimental angled deck).
All three of the US Navy's Midway class carriers were upgraded to angled flight decks during the 1950s.
http://en.wikipedia.org/wiki/Flight_deck
http://www.navy.gov.au/history/angled-flight-deck
The conversion programs for the carriers seem to have taken between 2 and 3 years. USS Coral Sea's conversion took 2 years 9 months, USS Franklin Roosevelt took 2 years, USS Midway took 2 years 2 months.
http://www.uscarrierhistory.com/index_files/Page3646.htm
No foreign powers made any particularly aggressive moves at sea during this period of refit. No foreign powers had anywhere near the number of carriers that the US navy had, even if many of them were being refitted in a fairly short window.