I second aethel on using the demo's. It doesn't give you the full scope of the game but at least gives you a feel for the dice system, the dark heresy demo is mostly combative which doesn't give alot of feel for the much larger investigation type game it is but at least you'll know if you like the system in general.
If you like the demo there are a few other free adventures on the support page. Edge of Darkness was a really well done one in my opinion and gives a better feel for the game and if I remember right includes the rules and is made for people that don't have the book. No demo for deathwatch yet but I'm sure there will be one eventually and everyones probably itching for it.
We always use mini's for our games but thats just something we've done in every rpg for years mostly brought about from DnD's attacks of opportunity and threat areas. And a battle mat is almost a must when your players start to use grenades.....I as a gm love grenades they usually turn my mobs into mush especially something like rogue traders filament grenade (they do on average more than twice what a 'normal' human could ever take) but when your pc's mess up a roll to hit with one its better to know exactly where it ends up. That way when the filament grenade from a player removes an arm from another player (my last game) it wasn't me being a **** that did it, the thrower messed up the roll, spent a fate point to reroll, messed it up again and rolled the scatter which made it right under another player (who failed to dodge).
If your group doesn't use area effect things, and rarely uses cover (which is a shame) you wouldn't need mini's as much but it helps to make combat more tactical.
Only dice needed are d10's preferably one as percentile, the d10's with 2 numbers on them 00-10-20 ect. but 2 d10's of different colors work too as long as your players are not the cheating type to say 'no the red one was my 10's not the blue one'
Character sheets/stats are fairly easy, the leveling system to me is the best of any game i've ever played. Instead of get N xp then get this whole host of abilities its a spend N xp on this Talent or skill. After almost every game my players can get something new even if its just a bonus to an existing skill unless they are saving up for one of the more expensive upgrades.
Only issue is as a gm keeping track of what every talent does....What does True Grit do again? Crap I forgot he had Unshakable faith, ect. But you have that with alot of games there just seem to be a much larger range of them than I had to deal with in 3.5 DnD.