Amalgamating multiple datasets with different variables coding
I don't know of an automated tool for this, but as a suggestion, you could look to using feature selection or correlation of all variables in a particular dataset against all other variables.

It depends on the direction that you are wanting to take your analysis later, but the second method will enable you to see variables that are highly correlated, and so might be good candidates for checking that they are duplicates? 

Also, not sure if you are aware, but there are a few R packages (memisc is particularly popular) that enable you to read SPSS files directly and then work on the data directly.

Sorry wont save you months of work though ... but might save you days ...