Filament collected on nozzle and hardened. Strategies to remove or replace nozzle?
I have printed successfully. This afternoon I updated the firmware. After the firmware updated I attempted to print a simple lid. It started ok and I left to walk my dog. When I returned the filament had collected on the bottom of the extruder. It hardened and now I am unsure how to remove. I have tried with a knife but no real success. Any strategies for removing filament that has wrapped around the extruder and dried? 
This has nothing to do with firmware.
You have a small blob of doom. Search for blob of doom to see how others have dealt with them.
Before doing anything, look at pictures of a clean extruder and note the position of the rather delicate wires that are currently hidden, if you damage them you will have to buy replacement parts as broken wires can't be rejoined.
Check your fan shroud, if it has distorted you will need a replacement.
To remove the blob:
Raise the nozzle temperature to the printing temperature for the filament in question and allow it to heat for several minutes.
If you are lucky you will be able to prise the blob open - more likely you will need to add heat from outside with a heat gun to aid the softening, sometimes it's worth using a soldering iron to carve chunks off the mass.
Use needle nosed pliers to prise this away; remove it in parts if it won't release the wires.
Once you have the worst removed you decide whether you need to disassemble the extruder to get at all the blob or perhaps you can clean up in situ.
After the cleanup there will be overcooked filament inside the nozzle so at least a purge and probably a cold-pull will be necessary.
Cheerio,