Switching from work permit to work permit

Hi there,

I have tried to read through all the posts to make sure this (perhaps) obvious doubt has not been asked.

I am on a 5 year work permit and plan to switch to another job. If I choose to try for another work permit (this job title will be different), and if it gets approved, then do I have to contact immigration and forfeit my first one and then apply for the 2nd work permit.

Just trying to get the sequence of how to do things. I know that if the new work permit is rejected, that i can still continue to work under the old one for the old employer.

also, does this mean that i will not have to leave the country?
does that mean that i have to apply for FLR? HOw much does that cost and how long would that take?

hope someone can help.

thanks.