Hi Mani,
There is no pre-existing cubes for the Field Service module in GP, that 's right.. Actually this question will cover 2 aspects :
1. you need to know what data you want to analyze out of the Field Service module, thus you need to know the data structure of the module in GP.
2. You'll to think about what data is going to be essential for your analysis of FS. This will also drive your cube structure in SSAS.
I suggest you start with a solid book about GP reporting tools (like the one at Pack Publishing), and then also dive in some good books about SSAS and MDX/DAX. There a training class at Microsoft about building and managing Data Whareouses with SQL 2012 (10777A followed by 10777B I think.. but it looks like this has been replaced by 20463 for SQL 2014 now).
Have a look into all the free Micrsoft eBooks available for download : https://blogs.msdn.microsoft.com/mssmallbiz/2015/07/07/im-giving-away-millions-of-free-microsoft-ebooks-again-including-windows-10-windows-8-1-windows-8-windows-7-office-2013-office-365-sharepoint-2013-dynamics-crm-powershell-exchange-se/
There is certainly something about SSAS like this one.
Good luck.