Background: 98 XC70 that is parked often and when driven is mostly driven short distances (less than 5 miles).

Issue: Car barely started the other day after sitting for a couple of weeks in 20 degree weather. I drove it for about 15 mins with everything powered off except the parking lights were on. Forgot to turn them off and after sitting for an hour the car would not restart. Got a jump, drove it home and noticed that the mileage had reset to zero...put a trickle charger on it and now the car starts up fine but all the dashboard lights come on and NO gauges work. After researching similar posts I'm led to believe its most likely the alternator, but would appreciate any advice to the contrary.
Thank you!

 

Good morning again!
I could really use a second opinion on the likelihood of this being something other than an alternator problem. Any help is very much appreciated.