If I (the buyer of services) mistakenly missed information in the contract can I update it with the correct info?

Yes, unless you (the buyer) have accepted a bid in which case the seller needs to modify the contract and resubmit to the buyer for approval. If no bid has been accepted then you can change the contract specification and any other information needed to be added or deleted and resubmit the service request (SR) for new bids. Resubmit a SR from the buyer can only occur one time. After one resubmit then the SR will need to be cancelled and a new SR submitted.