Are there alternatives to Microsoft Access?
Check out Linked Tables to SQL Server if you're running up against complexity requirements for your data.  Basically, as you are expecting, Access would still work as your front-end and SQL Server would work as the back-end.  For complex SQL statements, you can make use of Stored Procedures that you call from Access as well.  If nothing else, this could give you some more time to rewrite the Access application in something a little more robust like .NET (language/platform of your choosing).  Honestly though, if there's no pressing need to change out the Access application, keep it around if it's doing the job.  I support clients that run tons of business functionality off of an Access front end tied to a basic availability group on SQL Server Standard Edition for high availability.  It does the job just fine and it doesn't cost an arm and a leg.