I am new in this forum and my First post. and also new to RC. So moderator if i have post in the wrong section pls advise...

Q 1 - I am considering to upgrade my servo to a Hitec HS5085MG full metal gearing but i am aware is not a straight fit in situation and i would need to change the Aluminum Servo Arm Crawler to a a Losi A 99038 that fit well to the car.
Did any of you try this?
and is this the correct way to do it?

Q2. - I do experience sometimes the car stopping for no reasons and have the electronic speed control light flashing red, by unplugging and re plug the battery cable the car will re start and go.
Why do i have this problem?