Ordering parts to replace

I made the parts order:

• timing belt


• timing gear sprocket


• cylinder head gaskets


• valve cover gaskets


• valve stem seals


• front/back crankshaft seals


• camshaft seals and o-rings


• water pump, gasket and seal


• thermostat and gasket


• oil pump seal


• oil inlet tube seal


• timing gear sprocket


• intake/exhaust manifold gaskets

The price of these items add up to nearly 1/3 the price I paid for the engine itself. However, it's pretty simple to do the work right now when the engine is sitting on the workbench. However, once the engine is installed, doing the same work would require a heck of a lot more time and energy. Therefore, it's a matter of "pay me now or pay me later" I'd rather do the work now when it's easier.