What tools will I need to remove sprocket/what type will I need to order?
That will be a BMX freewheel tool you will be needing. Order a BMX style freewheel, count the teeth or get one with less/more teeth depending on how you want to be pedalling - higher cadence will need more teeth.

If you have access to a big vice then you can put the freewheel removal tool in that. Otherwise a really big adjustable spanner from some pound-shop will do nicely.