Reading the Param.sfo file:
Read @ offset 0x128 for Disk ID
Read @ offset 0x140 for Disk / Game Version
Read @ offset 0x14C for Firmware Version
Read @ offset 0x148 for Parental Level
Read @ offset 0x158 for GameTitle
Reading an ISO is too 'in depth' to explain in brief. I suggest you read up on ISO9660 format as it is a lot similar to UMD.