Can we use a known plaintext attack
Considering that you have 1,000 plaintext-ciphertext pairs, you should be able to.
Known plaintext attack(s)
Try applying linear cryptanalysis, DES is relatively weak against it.
Alternatively, you could try differential cryptanalysis; DES is usually considered to be relatively strong against it, but with only a single round you might still make some headway.
or would another attack be more advisable? If, which one?
Chosen plaintext attack
Do you have access to an encryption oracle? If not, then you can't perform a chosen-plaintext attack.
Chosen ciphertext attack
Do you have access to a decryption oracle? If not, then you can't perform a chosen-ciphertext attack.
Since the cipher is a reduced round variant that uses only a single round, you cannot use a slide attack.
You could probably rent a supercomputing cluster and simply crack the key with brute force. This is probably the slowest, most expensive, and least enlightening technique, but it will work against regular (not triple) DES.