Is the word preparo the same in Brazilian and European Portuguese?

No

While the dictionary definition, spelling, and grammar of "preparo" are identical in both Brazilian and Continental Portuguese, there is a difference in typical usage.

In Brazil, "preparo" is very commonly used to describe the process of preparing something (e.g., the process of cooking food or the process of studying for an exam). In Portugal, while "preparo" is understood, it is much more natural to use the word "preparação" to describe a process. In Portugal, "preparo" is more frequently reserved for the result of a process (like a medicinal mixture/substance) or the state of being ready.

Brazilian Portuguese Examples

1. O preparo da comida levou duas horas. (The food preparation took two hours.)
2. O preparo para o vestibular é muito intenso. (Preparation for the college entrance exam is very intense.)
3. Ele não tem preparo nenhum para esse cargo. (He has no preparation/training whatsoever for this position.)
4. O preparo do terreno é essencial para a plantação. (The preparation of the ground is essential for the planting.)
5. O preparo desta receita é muito simples. (The preparation of this recipe is very simple.)

Continental Portuguese Examples

1. A preparação da comida levou duas horas. (The food preparation took two hours.)
2. A preparação para o exame é muito intensa. (Preparation for the exam is very intense.)
3. Ele não tem formação nenhuma para este cargo. (He has no training whatsoever for this position.)
4. A preparação do terreno é essencial para a plantação. (The preparation of the ground is essential for the planting.)
5. A preparação desta receita é muito simples. (The preparation of this recipe is very simple.)