Discover MTU between me and destination IP

I believe what you are looking for, is easiest gotten via traceroute --mtu <target>; maybe with a -6 switch thrown in for good measure depending on your interests. Linux traceroute uses UDP as a default, if you believe your luck is better with ICMP try also -I.

A quick search with apropos mtu on CentOS5 turned out:

tracepath traces path to a network host discovering MTU along this path