If you search any of the running forums on other sites (coorunning.com, for instance) you may find some good advice about lodging and so forth, as well as answers to your other questions. Boston is an easy drive from where I live, so I've never had to worry about finding a place to stay when running the race.
Most people stay in Boston, as close to the finish as they can manage/afford, but you can stay outside the city and take the T or a cab. Buses take runners to the start in Hopkinton so no worries there. The town is packed with runners who meet on the grounds of the high school and have to wait for quite a while. Everyone walks to the start together and they guide you pretty efficiently.
Here are a few links:http://boston.marathonhotelguide.com/http://community.active.com/search.jspa?resultTypes=&dateRange=last90days&peopleEnabled=true&q=boston+marathon+hotel&containerType=&container=&containerName=&username=
I ran the race twice and it was no picnic. To this day, I can't explain what went wrong but they were definitely two of my most unpleasant marathons. The weather can be very tricky that time of year. On both occasions I had trained very hard through very cold winters here in New England, only to be met by warmer weather on race day. I think it was 2004 (my second go at the course) that the temperatures were blazing hot—close to 90º, if not more. No one could stay hydrated, everyone ended up with incredible blisters and bleeding feet due to the water the fans were spraying on the runners. My worst marathon time was that year.
Stay hydrated for days before the race, not just on race day. I do think the heat is the big gamble because you don't know what the weather will do. I found myself wanting to walk at about mile 17, which was really alarming. If that urge comes along in a marathon, it usually doesn't hit me until the last three miles of a course.
The first part of the course is a very gradual drop in elevation and this can do a couple of things: it can start you at a faster than advisable pace and it can wear out your quads for the later uphill portions of the course. Take it easy the first few miles, but not too easy. I've run up worse hills than the famed "Heartbreak Hill." It's not so much the elevation there as it is the timing in the race. It comes toward the last 1/4 and you're pretty wiped out by that time.
If you like a lot of screaming and support from the sidelines, this is the race for you. I find it motivating when things are going well, but when I am struggling there is nothing more irritating than a loud-mouthed Bostonian screaming something like "Get yer ass movin!" For me, marathons require a lot of concentration and Boston is crowded with both runners and spectators—you won't be able to run much for the first mile or so, especially if you're in one of the later corals with a higher bib number. You get tremendous support from the people on the sidelines, but I found it tough to keep my mind on my pace and other things which help me run a good race.
I have to say that running Boston is not something I regret, and I am glad to have done it both times—even when I was saying "never again" I was thinking, "I wonder how I will do next time, in better weather." And some people do just fine at Boston. It's a benchmark for a lot of runners—the pinnacle of standards for qualification—and when you earn a number by racing a good qualifying marathon, it feels fantastic, that's for sure.