I am currently in a two year landcontract. I would like to extend the terms for an additional two years until I graduate from college. Is this legally possible and what should I do? Thank you.

It is possible only if the seller will agree, For some reason you assumed when you signed it, that you would either have the money in full or be able to re-fi some where else.

So if the owner will not ( and there is no reason they have to) you will have to either re-fi some where else or you will breach the contract.