Have you gone through the Excel training in the training materials? All is there , you will soon get the ideas and dealing with data 
You even don’t have to open explicitly word doc as well just use “Word Application Scope” activity i.e. same like “Excel Application Scope” Activity.
You can easily see the available activities under that category like all available activities for word will be available under Word category and so on(Just make sure you have installed that package from package manager first). for activities guide -
SideNote- Replace text activity in word is case insensitive.
For your guidance here review this sample workflow. as @vvaidya suggested… it is basic approach and good one as well.
SampleWord.xaml (10.3 KB)
Let me know, if you need any help on this and any doubt if you have?
Regards…!!
Aksh