Hello:

Looks like I will have to start considering a new roof.
Live outside of Boston.
House is about 30 yrs old, original roof, and the foundation is 28' x 48'
Tri level (split type)

Haven't even thought about roofs in many a year.
So, let me please ask:

a. It's the original roof. Is it normal to place a second layer right over
the first, or must
the original layer be removed first ? Why ? Pros and Cons ?

b. For the dimensions noted, what might be a very approximate cost to do ?

c. What's a "good" brand (and type) of roof shingles to ask for these days
?

Not sure how they are specified; is it by shingle weight, thickness,
or... ?
What do I (probably) want, or what should I ask for ? (expect to be
in house for a long time)

d. I'm sure there are many questions to ask the contractors when they come
over for a look and estimate that I am not even thinking of. Can anyone
suggest what to ask, or what I should be considering also, please.

Much thanks; really appreciate it,
Bob