1300 to 1600

I’m thinking on upgrade my 1300 DP to a 1600 DP for 20 years...at least.
The engine was rebuilt 12 years ago and since I made about 10 000KM (6250 miles).
At the time I putted used pistons and cylinders because of the money, so I don’t
need to rebuild the engine only take of the cooling surround, the heads and pistons.
I never pull out the engine so I also don’t know if I will try to do it myself.
I will ask the price to a guy, whish his job is beetle engines rebuilding to know
if I will save any money.
My questions are the following:
1- Do I only have to buy new cylinders pistons and heads and valves? Can I use the
some rocker shafts and springs for example?
2- Want tools do I need? (this is my first concern)
3- I want to keep my stock Carb Solex 31 pic to keep the stock looking
4- Can we feel a hard difference between a 1300 and a 1600?

Thanks in advance
Joao
72 Super 1302