Well first, the prices for rad cap and tstat are absurdly high. Just go on Amazon and buy a set for 1/3 that price. But do you have reason to think you need either one? If you had no known problems prior to all this just flush it the best you can (drain all via orifices noted above), replace the coolant with 50/50 and forget it. If you can find the capacity of the cooling system, then just put in half that much in full strength antifreeze and add water until it is full. Then run it a while, open back up and fill if it will take more. Essentially do what 5030 said in post #13. Once you are 100% sure the radiator fins are clean and open run it ( 20 or 30 minutes, go mow something) until it should be at stable operating temperature. The gage should show in the lower 1/3 of the range. Make it prove to you there is some problem, if any.