Vancouver FIR meaning
FIR stands for Flight Information Region.  There is lots of information about these on-line, to the point that it isn't worth regurgitating it here.

However, the FIR should be the least of your concerns at this stage of your training...

If you want to fly "in and among the mountains" of the extremely rugged North Cascades, I would strongly recommend you get your Private Pilot Certificate first, then take a mountain flying course as a minimum before you get any lower than 1000' above the highest peak in a sector, and/or gliding distance from a wide flat valley floor with suitable emergency landing spots.  

Narrow valleys and downdrafts on the lee side of ridges are killers. 

I live up here in Washington state and have flown in the mountains for years, but they are no place for a beginner on a student solo.  Especially this time of year.