Yes, SPSS supports multiple methods of replacing missing values.
Depending on how you plan to approach your missing values, these can variously be found under (a) Transform -> Replace Missing Values, (b) Analyze -> Missing Value Analysis, or (c) Analyze -> Multiple Imputation -> Impute Missing Values.
However, imputing missing values correctly can be tricky and the process is often abused. Without knowing anything about your data it is impossible to make a recommendation but if you're unfamiliar with the theory then the following reference provides a pretty good overview of the current status of the research:
Graham, J. W. (2009). "Missing data analysis: Making it work in the real world." Annual Review of Psychology, 60, 549-576.