flush the core you'll be fine.

also leaving the heat fan on 5 and letting it warm, your helping to slow the heat up time. the core is a little radiator, you run the fan it makes the coolant colder. run the fan on one or two. you'l have warm car in 10 minutes.

or, just jump in it and drive after it idles for 2 or 3 minutes. all i do now a days. your'll save gas, they just drink it idling.