skilled migrant visa

[chiara]

Myself and my family want to move to canada.  We're Irish although we're living in the UAE at the mo.  My husband is a construction manager but only has a diploma in civil engineering, not a degree which, I THINK, is the reason he needs to have a job offer before being able to get a visa. 

How does this usually play out?  Can you come out there without a visa on some sort of temp visa and sort it out once you get there, or does it all have to be sorted before hand?  I've read the info but it's all a bit confusing.  Is it a good idea to do it via an agency?  Is there a good one in particular?  I'm totally clueless as to how to do this, advice please....