Engine rebuild

I have a 2009 Subaru Impreza Outback sport
hatchback with 126k. For the most part, I
performed routine maintenance in a timely
manner, but would run low on oil from time to time
and have a rougher driving style. The radiator
busted and that damaged the engine. I think the
engine is now on it's last legs (it's making a
rattling noise), so to speak and my husband says
if I need to replace the engine, I will also need to
replace the transmission and clutch. What kind of
cost am I looking at? I just bought new tires and
battery, which it needed. I love my car and am
willing to invest more money, but feel like I need to
look at the situation pragmatically so I can make a
decision I can live with.