you more than likely are going to find a crap load of junk in the heater box..
i have a roll of galvanized window screen which i cut and placed under my cowl to keep the leafs and sticks and all the other crap out..works great. looks like it was supposed to be there as well..
buy a good quality heater core..i used a roll of plumbers putty to reinstall the box to get a good seal and keep the rain water out..
i would replace the control vlave at the same time..
i used someone else's picture here
