Realizing adaptive and efficient peer-to-peer service-oriented architectures for MANET environments is a challenging problem. In particular, robust and efficient service discovery and service migration are critical in the constantly changing and bandwidth limited MANET environments. In these scenarios, service migration lays the foundation for self-adaptive architectures. This paper describes the agile computing approach to peer-to-peer service discovery and service migration and provides a performance evaluation of these functions in the context of the agile computing middleware. The experimental results presented in the paper show that applications built on top of the agile computing middleware are capable of opportunistically exploiting transient computing resources in the MANET environment.