I consider myself novice to answer this question, however I guess I can try.
1. Research, whether be it for products or service, per se there would no distinction. The process broadly remains the same... ie. Start with secondary research, move on to understanding the stake holders.. Develop a question/discussion guidelines depending on whether you are going by a quant or qual approach, analyse the findings and compile a report..
So as you see, there is no real procedural difference between research done for products or services.
2. However, we professionals are into making models for everything.. so taking a cue from there, I would like to refer to 4ps framework for products and 7ps for service. Moving from products to service, if the marketing mix would change, the research need would also change accordingly.
3. So my understanding would be, procedurally things would remain the same, however within each step the depth and extensiveness of coverage might change moving from a products research to research for services.
Hope it makes some sense..