Will this series of reactions work to produce potassium phosphate? I want to end up with a solution or anhydrous sample of potassium phosphate with which I can grow larger crystals. I want a challenge and something to do so I don't want to buy potassium phosphate, I would rather make it myself.

I don't have access to a lot of chemicals but I do have a fair amount of monoammonium phosphate, (or ammonium dihydrogen phosphate), from a crystal growing kit. I plan to heat this until the ammonia is released to leave behind phosphoric acid to which I can then add water to have an acidic solution. I will then dissolve potassium carbonate from corroded alkali batteries into water and add this to the phosphoric acid. The products will then be carbon dioxide, water and potassium phosphate.

My question is will these reactions work and how easy/difficult will it be. I am sorry if this makes no sense at all because I have done my research for this on Wikipedia and it isn't exactly a 100% reliable source. Thanks.
Getting phosphoric acid by heating ammonium phosphate probably won't work since it requires temperatures above 200°C where phosphoric acid will start to vaporize and decompose.

A better approach might be the reaction of ammonium phosphate with potassium carbonate. The ammonium carbonate formed by this reaction decomposes at much lower temperatures (> 60°C). However, heating will produce corrosive, irritant and toxic products (ammonia, phosphoric acid, phosphorus oxide), so I do not recommend doing such experiments.