Opensource tools for inventory and troubleticketing

Hello everyone, I work for a small service provider starting to offer MPLS services between Europe and several african countries. At present time we own a small Cisco network, but we are starting to need a better inventory of services and network resources and better troubleticketing procedures. We can not afford acquiring complicated and expensive tools at present time.I would be grateful if you could recommend me opensource tools to cover these needs. Thanks in advance Kind regards Octavio