Heater Core leaks...... tips, tricks, suggestions?

[G3KKO]

Well.....after a few minutes running....she pukes coolant from the a/c drain hole..... guess I will be pulling the HVAC box out..... aside from the SvcManual..... any advice?? I will be purchasing a complete over haul gasket/seal kit and evap core and heater core.... no more leaks...period.
Thanks!