Cisco 2921 setup

hi guys hope you are well.

ive got a customer who has had a 100mb leased line put in.

bt have given him a Cisco 2921

ive never played with a bit of kit like this before.

for reasons im not going to go into they have a server there that we are decommissioning,
 which will leave us with 30 pc's on a network. they just need internet access, access to a nas box and also there will be 9 of those pc's using networked sage.

1) do  i need to buy another router to put in front of this or will this piece of kit do all the routing and dhcp that i need?

2) if so, how do i configure it - does it have a web UI and is it fairly straightforward? are there things i should configure on it other than the dhcp if so, what are they?

3) is it worth putting in some kind of dns server - if so whats the best thing to do?

thanks for your help.