Q: I have a 45 amp alternator in my plane.
If change the 35 amp breaker in the panel for a 60 amp breaker. Will this work with the Mini power panel?
Proper sizing of the alternator breaker should be at or less than the rating of the alternator's maximum output. In your case the 35 might suffice if your maximum power draw is 35A or less. Remember that the alternator circuit breaker is there to protect the alternator from the airplane loads - you don't want to over rate this case...
Suggest that you look at a Tyco W23X1A1G40 - Aircraft Spruce catalog# 11-04121. This is a 40A breaker that will do fine for you if the 35A is not enough. Personally, I would use the 35A part. It is probable that it will take care of things for you with out issue.
Q: Is a master solenoid needed with the mini power panel?
Yes, a master solenoid is needed with the mini power panel.