Hi Hoquista,

I'm new to the board, too, but I think I can answer the first question:

Mercenaries show up immediately. Selecting the merc units you want (by left clicking on them) puts them into the cue boxes at the bottom. To actually hire the devils, you have to click on the hand to pay them.

Mercs last as long as any other units - until you disband them or they die off - but be careful, they cost more per turn to maintain.

Q2: Don't know...I go patchless.