What's the difference between the endings "ou to suru" and "- te miru" in japanese when trying to do somethin?

Question:

I mean, what''s the difference between saying しようとする and してみる???
Is there any difference? Can you explain it to me?

分かる為にこの和文を直してくれて下さい。
(Please correct this japanese sentence so I can understand).

What I want to say: "I've never exchanged letters before but I'm trying to write a letter for a japanese friend who lives in tokyo".

文通をしたことないのに東京に住んでる日本人の友のため
手紙を書こうとしてる。

Should I say 書こうとしてる or 書いてみてる??

Please help me.

Thanks.

Answer:

手紙を書こうとしてる- you are just about to start writing to your friend
書いてみてる - you are making an attempt. you are not sure if you could write properly or not, but you are trying to write, you are thinking of trying. may be you have never dane that before, or may be you started learning so you want to give a go with it to see if it will make sence.

v+te miru - it has a implication, that you are trying to test or make attempt.