Help Needed with project

Basically I need help with this procedure.

"A binary file needs to be decoded, I know the file contains an Ethereal capture of an ICMP packet. I therefore know all the encapsulation layers and need to decode the binary frame into something like a Text representation for analysis."

If anyone can understand this and point me in the right direction, then I would be very grateful, cheers.

Look up how Ethereal stores packets in the logs (it's probably standard PCAP format). It will contain an ICMP packet (ping is the most known one). Look up the fields.
Then, you just need to parse those fields and output whatever information they give you.