Document and manage a WAN is a wide open objective, Paul. You need to narrow the scope a bit.
First, what are your objectives?
Document - for what purpose or purposes? Who will use it, and for what? Are you recording information, or providing information? If the latter, what information and to who?
Manage - what do you want to include in this? Change control? Automated configuration? Fault identification, fault analysis, fault resolution? Disaster recovery? Trend analysis? Repair action assignment, status tracking, resolution record, trend analysis? In-house or outsourced?
Cost parameters - do you have a range, or value based on costs of not documenting and managing?
What constraints are you faced with for implementation, support, and use?
My recommendation is that you define your business objectives and business requirements first, and then set technical objectives to support these. The technical objectives will define your technical requirements, which you can then use to select the management and documentation package or packages that meet your needs in your environment.