Take a look at the Excel Importer module in the App Store for the easiest way to import from an Excel file - you will also need to import the Mx Model Reflection module to use this. Often it is easier to create a temporary entity matching your excel data structure and import into that, then write microflows to manipulate the imported data and push it into your final data entities. You can also import data from MS SQL and Oracle databases using the Database Replication module. In your case, creating a spreadsheet from Access and using the Excel Importer is probably the way to go.

I'm not sure what exactly you mean by executing queries. Every time you display table data in a datagrid you are performing a query, expecially if you use search attributes. Or you can produce datasets using OQL queries, or you can perform retrieves in a microflow... all these are queries. Or outside of mendix, you can perform queries against the data with the client of your choice directly against the database.