This is a combination of current-state to target-state and scenario planning.
You have developed a current-state map according to criteria and a target-state according to where you want to go and be. You have done a gap analysis between the two.
Then you have a choice of implementations that will take you towards the target-state, according to strategic or other considerations (which is why you're upscaling your MS Access to a multi-user environment).
Then you identify targets that your implementation will impact, for example, stakeholders, processes etc. Your targets need to be understood on more than just a one-dimensional level (for example, with stakeholders, look at all the models used to analyse them).
Then you use various models to demonstrate the impact (benchmarks, perception maps, qualitative, quantitative, processes, financial etc).
Here, it's using all the methodologies of scenario analysis. Various scenarios lead to various outcomes.
For example, stakeholders can initially be analysed as hot and cold and various degrees in between. You can show how the particular project action plan moves cold stakeholders to hot, moves resistant stakeholders to aligned etc.
An "Impact Analysis" is much more complicated than these two words make it sound. There are hundreds of potential criteria that your implementation will impact. You will likely have to include financial impacts, so a good idea of financial ratios will help etc etc etc.
In a way it's common sense, but you won't make it "professional" unless you apply the models to it (you won't be taken seriously if you use uneducated terminology and structures; your bosses won't think you're "adding value"; you won't be offered a job or be promoted), which indicates that you need a good understanding of them. See www.clickok.org for a range of models.
Hope this helps.