I would try to find out what your company found out during the due diligence process of buying the new company.
- such as certifications like ISO9001, ISO27001, ITIL, etc.
- This might give you an idea of the company general approach and culture.
Then I would suggest that you ask softly and listen carefully for the answers, and not look to change what is not broken.
- e.g. how are the IT systems structured? What documentation on architecture and design is there?
And then try to understand the people who are making it work already and their strengths and weaknesses.
I would go gently at first, unless your boss has asked you to do something specifically such as IT integration with your current systems.
Otherwise, changing the IT department a lot could upset the company you have just spent good money on buying as well as their customers.
My employer was bought recently, so we have been going through IT integration and it has not been totally smooth for people outside of the IT department.
I hope that this is useful.