Have you looked at the "SSMA" tool from Microsoft? It is a reasonably good "SQL Server Migration Assistant". On simple databases its a point and click and you are done. On more complex systems its at minimum a great first step.
I have migrated several major customized access database/applications used by several local municipalities with success.
One word of caution: Watch out for the "Denial of Service" attack that Access will do on your SQL server. The default login for Access is a user named "Admin". If you use windows authentication against SQL, it will attempt to authenticate first as "Admin", then using the users credentials. The combined number of users running your application can form an effective denial of service attack (even though it is unintended). The only method I found around this was to not use windows authentication against SQL.