The first thing is to identify what you have and confirm it is actually working. You can start by checking if there is any output before and after the charge controller. You may end up removing the panel to see if it still has a tag on its back side with the info.
A panel of that age and size isn't going to be a power house, more of a battery maintainer I suspect.
How much space do you have for panel/s? What kinds of things are you doing to drain your battery and how is it that you charge your battery now, before, during and after the trip?
Once you know what you have, how much room and how much power you need you can start planing. Panel prices have come down to the point that I wouldn't try to match up the old panel and start fresh. I would shoot for 120w and up depending on how much room you have.
I went the easy route and left my panel portable so that the trailer can be in the shade with the panel in the sun. You could get two smaller panels and hinge them for easier storage.
I do agree with Roy in that more battery is needed with solar. I can get a week off of my bank with the reduced output of the solar in cloudy weather. My original grp 27 is fine when we get sun for a few hours but will only last 3 days in bad weather.
Good luck and look forward to seeing you when you have more info.
2011 GulfStream Amerilite 25BH
2003 Ford Expedition with 435w tilting portable/ TS-MPPT-45
750w solar , TS-MPPT-60 on the trailer
675 Ah bank, Trip-lite 1250fc inverter
Sportsman 2200w inverter generator