You don,t need to take the engine out to replace some leaky gaskets.
You said you needed the car and can not afford to have it parked for a few days when you do the repairs. Why don't you rent a car for a week or two while you do the gasket job?
Your plans (buy a donor car and swap engines) are not economically logical. Assuming your front-end cover is leaking, having the job done by a competent technician would take less than a day....still cheaper than buying a donor car and do the job yourself.