To be honest mate if you are buying second hand dont bother, it just isnt worth the risk. I have spent all weekend rewiring and escort cossy for a customer and if you know what you are doing and have the correct kit its just a matter of time. Im an electrical designer for a major OEM so its easy for me and i have all the kit. If you yourself know you stuff give it a go, however if you are short on electrical knowledge you could end up with a whole load of problems so be careful. I see so many burn outs and meltdowns though the lack of knowledge and understanding its untrue.

Hope this helps in some way