You dont need to upgrade to be attached to an mpls network mate. Your routers are what we service providers call CE-routers. You have a few choices, depending on your SP that is. IGP can be either static routes, bgp, eigrp, ospf and rip v2. OSPF and EIGRP are not offered by most SP's but BGP, RIP2 and static usually are. All you need to do is configure your routing protocol and shove an IP address on your WAN connection and you shall peer with the MPLS-PE router.
HTH