Hi, As you mentioned all the web services are available. I have large experience in this kind of apps. I already know all the aspect we needed to complete this project. go for it and you will never disappointed at all and you will definitely found the quality of work like flow, designs, simplicity, quick responsiveness in application. please find me on skype "suproid1". Time to complete the job is depends on how many web service methods are there for calling.
HAVE A NICE DAY.