Congrats Erobin223 - 

Regarding your how long to book a photographer question, I think that depends on what you want him/her to capture.  Some people really want lots of getting ready pics followed by coverage of the ceremony and most of the reception.  Based on that, you are pretty safe with booking 5-6 hours [1 hour to 1.5 hrs for getting ready pics, 30 min-1 hour for ceremony pics, 1hr - 1.5 hr post ceremony & the rest reception pics].

My photographer suggested going with no more than 4 hours and I agree. I don't want a lot of getting ready shots.  Maybe a couple of my mom & sister helping me with my dress, the first time my dad sees me in the dress, then ceremony and post ceremony shots. Reception-wise, he agreed it is a waste to have them there for most of it so I am having all the key events like the 1st dance, parent dance (me & my dad, fiance & his mom) followed by toasts and cake cutting within the 1st 30 min-1 hour of the reception so he can get those shots and be finished.  He also suggested what time I should schedule my ceremony to ensure we get the best light & sunset shots post ceremony.  He likes shooting the reception in the dark.  We further felt we'd made the right choice after receiving his candid and helpful feedback/suggestions.

As for more than one photographer, it helps in terms of making sure they get all the shots you want.  However, I'd make sure the assistant or co-photog has the same "eye" as the person you are hiring. My photog has an assistant who shares his "eye" & is included in his rate, so I'm ok with this.

I'm not sure which photographers price negotiate as none of my top 3 picks did so.  I ultimately went with the one both my fiance and I liked the most.  He doesn't price negotiate but it's understandable - he charges a pretty reasonable hourly rate. He is not one of our resorts preferred vendors so we have to pay the outside vendor fee for him to come onsite. 

I'm getting married at a Karisma resort and found two local florists that other Karisma brides have been happy with that are much cheaper than Karisma's vendor Weddings by Lomas.  I'm not sure about delivery fees though. 

Hope this helps!