the rule mentioned means the dice are changed immediately after they are rolled at any point, and that they are changed before Any further modification. if they are rolled again, they are changed again before further modification. doesn't say this is not the casecase so it is assumed card text prevails. however, other abilities such as marksmanship or mercenary copilot function as normal

This is a subject of a lot of debate. There's some good back and forth here:

http://community.fantasyflightgames.com/index.php?/topic/87083-faq-heavy-laser-cannon-target-lock/

They cornered James Kniffen at Gen-Con (it's a post on the internet about a conversation, so it's not exactly 'official'):

http://teamcovenant.com/buhallin/2013/08/20/gencon-revelations/

The gist is that CrookedWookie has it right, the re-roll is not the same as a 'roll' so the HLC text does not apply. As an extensive user of the HLC, I've got a pretty strong confirmation bias on this one.

Rich