Cleaning Pentax-F lenses?

[John EW]

Hi, I've just received a Pentax-F 35-135 smc  from Ebay that seems to have 
quite a bit of internal dust.

Is it difficult to dismantle these lenses for cleaning? - and, perhaps more 
to the point, is it difficult to get them back together properly?!

Any other less drastic suggestions for shifting dust on internal elements? - 
I've considered using compresed air - is this viable?

TIA