book time is 7.3 hours on the clutch, so depending on his labor rate, $1000 sounds fair to me.
Of course, I keep hearing how all these jobs are so easy, these people that never have done one can do it in 30 minutes
Whether or not the symptoms are completely related to the clutch failure, I assume that the mechanic did find the clutch is bad. If thats true, then you have 2 issues. If its not true, then you need to get a second opinion.
Clutch failure seems to confuse people very often. I can't tell you how often I have to argue with people, the reason their car no longer moves is the clutch is toast, when they want me to throw fuel filters and sparkplugs at it. I'm not questioning your relaying of the symptoms, but if the mechanic is positive the clutch is bad (how bad, is the question IMO) then it could be related, definitely.
In short, get a second opinion.