tint...vkool or 3m

[sds]

hi,
sorry if its a repeated post.

have decided to tint and narrowed down to vkool or 3m


1.which one is better?cost?how much for e60
.
2.will my garmin gps still work?

.3 which work shop does it best.contacts. dont want to go back to remove dirt etc.

4.legally its 70% front windscreen and front windows..what about rear?as i my ride is black.
TIA