Catastrophic print failure - don't even know where to begin to repair this
Okay, so I was printing a large flat tabletop piece on my MK4S, and some hours into the print the print must have popped up in one corner, because the extruder head pushed so hard against it that the magnetic plate came loose and it and the print flew off. The extruder kept spitting out PLA and by the time I heard the unusual sounds it had formed a glob about the size of a misshapen golfball completely encasing the extruder. It took good amount of time to chip/melt off the PLA to free the nozzle, but by the time I finished I may have severed a wire.
Where do I even begin to diagnose/repair this? I'm terrified I'll have to replace the entire extruder assembly (I'm kinda figuring I'll have to break it down to make sure I got all the PLA off). Does anyone have a diagnosis step-by-step, or should I just follow the installation instructions backwards? Can I buy a new extruder assembly? 
RE: Catastrophic print failure - don't even know where to begin to repair this
Personally, I would proceed as follows:
- Replace the temperature sensor for the heating block
- Check the heating element for the heating block to see if the wiring is OK
- Remove the nozzle and check if it wobbles or runs unevenly; if so, replace it
- Check the remaining cables to see if the insulation is OK
- Make a first layer print to see if the load cell has been “pre-damaged.”