Hi, Rob, and welcome to the forum. You came to the right place!
The answers to your questions are basically what this forum is all about. There is plenty to read, I realize, but if you want the short answers, here they are:
a) Is there even a consensus among Muslims as to whether abrogation is legitimate theology?
e) Is there a consensus among those who believe in abrogation as to which verses have been abrogated?
No, there is no consensus, neither on the doctrine itself nor on the individual claims.
b) Which verses if any have been abrogated?
Those who claim abrogation had claims anywhere between 4 and more than 230 verses abrogated! We counted so far 379 verses claimed abrogated, and we've shown in this forum that none of the claims can stand.
c) How do you know if a verse has been abrogated?
The only way is for God or His Messenger (PBUH) to tell us and neither of them did.
d) If a verse has been abrogated is it still in the Koran?
Yes, and that is one of the weirdest things about the abrogation doctrine as it clearly doesn't make any sense.
f) If a verse has been abrogated is it replaced with a verse that has a similar meaning eg one that commands you to do good deeds?
Not necessarily. Some scholars said that a Hadeeth (saying of Prophet Muhammad, PBUH) may be the abrogating text.
I encourage you to read the topics that address those questions in much detail and ask questions.
A candle loses nothing by lighting another candle.