Hey My Dear Friend
If UI/UX is ready then will not take more than 15 days.
I have found your requirement regarding integrate SOAP API JSON/GDS with your system and i am applying here as i have 9+ years of exp in this domain and in that i have worked with almost many GDS like sabre, reconline, galelio, amadus etc. you can check in my profile about detail.
1) What is your past experience working with and integrating an Amadeus and/or Sabre SOAP XML API?
>> i worked with Sabre API recently, you can check my profile.
2) Have you ever worked on a project or application that required conversion of a SOAP API into a JSON environment?
Yes i have worked with almost all the OTA, GDS so XML and JSON, i am expert in that.
3) What, if any, experience do you have building a plugin to integrate with an existing application?
Yes i have build many API which existing system can just call and get required data using API.
4) Are you an solo, independent dev?
Yes i am independent developer as well as team, whatever you want it is available.
5) Do you have any initial questions for us?
in Sabre which API you want to connect? have you Sabre credential ready for development?