99StanG97

Hey guys! I'm new to the forums and am loaded with questions that i'm sure you guys can handle So i have recently acquired a 1999 Mustang coupe 4.6 auto. It was my cousins and he surrendered it to me for my 16th birthday. It was his 16th birthday present as well, though he has no knowledge of cars... He claims he was driving when the engine seized on him, by lack of putting oil in it. Anyway, however it happened its been sitting in his driveway for four years. Untouched for the last four years its thoroughly seized now. The trans is leaking underneath and the crank pulley is surely not moving anywhere. Tried freeing it. But to no avail its pretty stuck.
Anyway, I came across a 2001 police interceptor 4.6 motor and trans for sale. Asking $800 for the pair, 120000 thousand miles on them. Supposedly running.
So my question is, will it simply bolt right into the stock motor mounts on my Mustang? Or would i need to buy new mounts? Same for the Transmission. Would that bolt right up? Or bolt to the current transmission in the car? (If its not garbage as well). I wan't to say the motor I'm looking at is a PI but i'm not sure. Believe that was in all 2001's etc?
But that's my question, would it be to much work or would it be alright to do? I've been looking for an original 4.6 out of a mustang but haven't been able to find any around my area or surrounding states. Via Craigslist that is. I know its no walk in the park, it's a project. But its free and also not my first motor swap. Did a 94 Mustang GT 5.0 swap (Blew it up, replaced it with an original). So i know its not easy, but not to hard with the right tools and resources . That's it for now!
Thanks in advance.