Brake piston compress/bleed and FLAPS question

[stateofidleness]

Gents,
Going to re-attempt my brake pad swap tomorrow. The first time resulted in failure as I could not get the pistons compressed (at all!). I'll be picking up a tool for this tomorrow, but also was wondering some things..

If the tool fails to work, what can I expect by opening the cap to the reservoir, and also, if I open the "bleeder valve" on the caliper itself, does this mean I'll need to bleed the brakes? I really want to avoid having to bleed the brakes as I have newer fluid in it and it brakes great at the moment.

Last question, does the local FLAPS carry a correct "cabin" filter for our cars or do I need to order it online/stealership it?

thanks!