Paizo the publishers of pathfinder made this site apparently
www.d20pfsrd.com/
which has all the content of the books they published (and not just core) as well as third party information and a clear distinction of which is which in case you don't want to include 3rd party stuff.
Also in my opinion SRD's are 1000% easier to navigate than the books, so even if you require books at the table (some DM's don't allow computers which is a very reasonable rule and I try to keep mine off as long as no one's looking up rules even if it is allowed) having it available to the players when they are at home saves them time, and it's all marked with which book it is from.
My group just switched to pathfinder from 3.5 and I have to say I like it better for many reasons, there are a few things that I think 3.5 does better, but overall they're both fun and I know nothing about how to play 4.
I think for our group almost everything we've used if you are going to use physical copies has come from the core books advanced players guide and "Ultimate Magic" (again this is pathfinder)
Basically the info I need is what do I need to get started?
I'm going to assume you have 0 DnD knowledge for my answer because it seems like you probably have some, but I don't want to assume knowledge and leave something out.
To play:
Books (or if you allow laptops and srd, but discourage players from using computers unless actually looking something up is a good idea, especially with n00bs)
Dice(I'll assume you have plenty of access):
-d20 (1 or more per player)
-d100 (i.e. 2 d10's per person that are not physically identical)
-d12 (you shouldn't need more than one for the whole table)
-d8 (per player)
-d6 (you'll want a bunch, at least a few per player as even midlevels you may need to roll like 10 at once)
-d4 (any caster will probably want at least one, extras don't hurt)
Minis (again I'm guessing you have access):
- 1 per player and maybe if they have animal companions or familiars.
- if you're trying to save money (which you'll probably have plenty of minis unless the warhammer ones are the wrong size) dice work pretty well... i.e. 6 goblins attack the question "which one?" can be answered by the number face up on the die, easier on the DM, but if you've got the minis use minis.
Game mat-(square grid about 1" squares, laminated or otherwise erasable is best, or we used to use chopsticks to make walls so we could rearrange them because that was faster than drawing a new room all the time.
Paper and Pencil for everyone.
Pre-written campaign (optional) - some DM's prefer to run a pre-written campaign in a pre-written world, however many DM's like to make up a world and a story and there are plenty of places to advise you should you chose to write your own campaign.
Anywho, first time DMing is not easy, DMing with little play experience is not easy (though the first DM couldn't have had any play experience so it's possible) and DMing for newbs is not easy so as you approach game day I suggest you seek advice from anyone you know who plays.