A DSA 1024 certificate will not be very easy to crack, not even having a high performance cluster at hand. An exception might only be if generated using weak random data, for example because of the Debian random flaw.
If you have lost control over the private key, and do not have a revocation certificate, you cannot do anything about it. Key server data cannot be deleted, and you cannot modify or revoke the key without having the private key (or as a special case, revoke it with a revocation certificate.
To designate that a key should not be used, you can issue a revocation for your old key. Client applications like GnuPG will not consider it and mark the old key as revoked, but most of them will at least issue a warning (so other users have a hint that something is fishy).
Generally, always generate a revocation certificate immediately after creating a new key, and store it in a place you will not lose it (ie. printed on a piece of paper, maybe inside an QR code).