Can I hook up these light fixtures on my own or do i need an electrician?

I already have a light fixture hooked up on the ceiling i just want to switch it out with the new one. There are a lot of wires and a ground wire. Do i need to hook the ground wire to both brackets on the fixture or will one be OK. I have never done this before so I dont know if i should just leave it to an electrician or do it myself since their already is one hooked up.