If I decide to tkae a 6 unit course, will this be for 6 weeks like the other courses, or because it's a fully ear course it's 12 weeks?
Since it is a combination of two courses really though, would i be taking them together or separately? (ex. linguistics x2 or psychology x2 -- similar to 1x03 and 1xx3 offered at Mac, but these are for U of T)

A 6-unit course would be 12 weeks, since it's a full year course normally.

I'm a little confused about what you're asking in your second question though...

Assuming 1X03 is a prerequisite for 1XX3, then you will be taking them separately, assuming you pass 1X03. 1X03 will be offered the first summer term (early May to mid-June), and 1XX3 will be offered in the second summer term. (Late-June to early August). Since each courses is offered only once in the summer term, it doesn't really make sense for them to be offered at the same time if one is a prereq for the other.

A six-unit course shouldn't be looked at as a combination of two courses though. It makes sense in terms of workload, but keep in mind that as far as I know, there isn't a way to get partial credit. This means that it's an all-or-nothing kind of deal, so you either get the full six units or none at all.