An esteemed forum member sourced and installed a stock replacement for mine via bursons for around $350 iirc.
There's less expensive versions on eBay.
Iirc manual and auto are different part numbers...
It's very diyable. Budget an extra $120 for 2x big bottles of Subaru genuine green coolant.
Upgrades for very modded cars include the mishimoto alloy radiators for extra capacity and cooling headroom.
In the meantime use an obdii plug and app to keep an eye on your temps, eg torque or better, btssm.
The ECU temp monitor is more accurate than the gauge.
Clean the area of dried coolant so you can pinpoint the source, eg seam or hose.
And keep an eye on the coolant level!!!