sony xperia z1 : purchased in china

Hi Friends! I need your help. I purchased a Sony Xperia Z1 in China couple of years back. However, I could not use much after coming back to India, my home, as it does not have Google play store, Google map etc. I tried to load them from some other sites but after loading, these apps do not run. Later, I came to know that this is because of China's firewall policy and these apps are not permitted there. However, I want to use them now in India and could not use the phone to its capability. I was told that it is possible to flash the ROM with international ROM after rooting and unlocking the device. And then phone would run all the Google/Android apps. I am not an expert in such processing of the phone. However, I am technical person and use the computers quite a lot. It would be great if you can give step by step method and the sites from where to download the applications/ROM etc.