Question: Below are just 2 example sentences for the general format '[phrase]地给[noun][verb][phrase]'. 

1. 他十分坦率地给我讲了他的故事.
2. 他很不情愿地给了我帮助.

This type of sentence is very common in Chinese. I would like to know if, generally speaking, it is acceptable in Chinese to replace '给' with '替' or '为'. If you are Chinese, would you find that acceptable in most, if not all, cases?

Answer: 
Grammar only:

In the case， "他十分坦率地给我讲了他的故事". We can trim it, then we have "他给我讲故事". You see it ends with "讲故事" (vt+noun). You can also change the order: "他讲故事给我" to make it "vt+noun to someone".

他很不情愿地给了我帮助 can be trimmed as "他给我帮助". You see it ends with "帮助" (noun). It is the object of 给 and 给 is vt.

In case 1, if you replace 给 with 替 or 为, then the grammar is OK but the meaning may be changed. Using 为 is OK because you change "to someone" to "for someone". But if you use 替 here, the meaning is changed to "instead of someone".

In case 2, you cannot replace "给" with other characters since normally if you changed vt, you changed the meaning.
他十分坦率地给我讲了他的故事. Okay

他十分坦率地替我讲了他的故事. Okay

他十分坦率地為我讲了他的故事. Okay

他很不情愿地给了我帮助.okay

他很不情愿地為了我帮助。wrong

他很不情愿地替了我帮助。wrong

when u are wondering 給 or 替 or 為, 
Choosing 給。
I come from China.Trust me:)