As long as your contract for deed permits you as CDholder to sell / vend your interest to another party ,there is no reason you can not do this, As part of the deal I would suspect the cd buyer would bear cost related to searching your title to make sure it it clean and has no errors as well as cost related to transfering it but they will be buying it from you at a discount , the discount likely will vary according to how many installments are due, the interest rate of the CD the longer the contract is I suspect the deeper the discount would be since the new CD holder would have a longer payback time. If you can come to a agreement it certainly is one way to have a lump sum payment and no more risk to you. Another option if you need to do it can be to sell off X number of your due installments to another party , you still hold the CD that way. ( last property I was in the couple I bought from went that route when they had a short term need for cash, it did not change to whom I made my PI payments)
