I need a document explaining the advantages and disadvantages of converting point to point connectivity to MPLS and the plan / suggestion to overcome the disadvantages
Converting a network that consists of point-to-point links to run MPLS can have benefits. This is regardless of the type of links you have in the network.
One starting point could be this one:
The big benefit that comes with deploying MPLS in your network is the ability to run the MPLS applications. Here are the most important ones:
-MPLS VPN - Layer 3 (with multicast)
-MPLS VPN - Layer 2 - point-to-point or point-to-multipoint
-MPLS Traffic Engineering - point-to-point or point-to-multipoint
Each of these have their benefits, while running over a one common network : an IP network with MPLS enabled.
The most important benefits are:
L3 VPN : obviously gives you seperated VPNs, with the possibility of overlapping IP subnets
extreme easy provisioning of layer 3 VPNs
L2 VPN: supports transporting most supported layer 2 protocols, even protocols with clocking information
MPLS TE: steering of traffic through the network and extremely fast traffic protection
These are just the most important ones.
All of these applications run on one common network, while before MPLS, one needed to have multiple carrying networks (e.g. one Frame-Relay network, one ATM network, one IP network) in order to provide all the same functionality.
From point of MPLS customer: cheaper is good argument .
Benefit I see is that as Luc write... you can change L2 link to L3 as you need, you can have multipoint connection without any HW upgrade (so very cheap and very fast upgrade). Benefit is that you can upgrade provisioned speed until full speed of interface without problems too (HW is cheaper if you get Ethernet from provider).
Other thing is internal structure of providers network (the one that sells you point-to-point link can have more stable devices in its toplogy... MPLS provider can even have Mikrotik as core devices )