You, apparently accidently, just posted your private key to the forum. Since you should never give your private key to anyone, I deleted that post. However, others may have already captured your private key before I saw it. Therefore, for your own security, you should generate a new key for your use, and for best protection of your security, you should revoke the old key and distribute the revoked key. Anything you currently have encrypted to that key should now be encrypted to your new key instead, if you want to be sure it is still secure.
Having your key block does not tell me if your key is set to Implicit on your machine. If you reviewed its key properties, and All Keys, and see that Trust is actually set to Implicit, then it is in fact set to Implicit on your machine.
There is full compatibility between PGP 8 and PGP 10. The only potential problem is if the PGP 10 user generates a new key using algorithms or hashes not supported by the old PGP 8 version.