About how closely could I expect a field point to be sighted inas compared to a broadhead? In other words, will they bothhit inprettymuch the samespot on the target?(if I do my part)

Depends on how well your bow is tuned. Any bow can shoot field points concistantly even if it's radically out of tune (I knew a tournament archer that purposefully tuned his rig for a 4" knock high left tear through paper.) Broadheads are a different story, if the bow is out of center shot they will take steering control of your arrow and go wild. I get the bow shooting tight groups then fine tune my rest to get the broadheads and field points shooting the same point of impact.

A lot depends on your setup and how well it's tuned. Your broadhead also plays a big role. My link should get you started.
http://www.broadheadtests.com/TUNING.html

it depends on broad heads and tuning of your bow

after 5 shots link goto eastons homepage and download their bow tuning guide. follow the steps for "broadhead tuning"

if followed and all works out properly you should beable to randomly choose FP arrows and BH arrows and nail the bullseye with them reguardless. it can be a pain....but its well worth it. i can practice with FPs in the season...saving me from dulling BH blades and chewing up a BH target any farther...i declair 1 BH my practice BH and shoot it on ALL my arrows to make sure they all fly true. even months later i can still shoot both...kinda surprised me...figured something would move!

also your arrow spine has to be good or you have heck getting good arrow flight...just something else to think about. if thats good all it will take is verrry slight adjustments to the rest and/or nock to fine tune...i thought it was a miricale to have BHs and FPs hit together at first....seemed impossible for a while..