525d's are scarce very scarce most are low spec , you'd have a lot better chance comimg across a high spec 530d sport make a great daily they have bags of torque great for long hauls or nipping in and out of traffic although around the city mpg can be nearly as low the petrol equivalent fairly reliable and robust car main cause of concern are swirl flaps (not sure if manual had them) just get them sorted immediately if you do buy

5k should buy a good e39 theres not many even above 4k so you could put the extra into some suspension or something along them lines I wouldn't get too hung up on the sat nav its very dated at this stage being close to 15 years old