I don't have any Liberty experience but 200k miles is a lot for any vehicle.
But, if the vehicle was well maintained, oil, filters, and other fluid changes, brakes, tune ups, this can go a long way.
Decide how long, years and miles, you plan to keep the vehicle.
Do you plan to stay close to home, meaning if your have a breakdown, do you have a support network. I had a son with an older vehicle away at college several states away. Service and breakdowns were at nightmare and expensive.
I see your 15, so I guess this is your first vehicle and going to use it while at high school. If Grandpa is giving you a deal on it and if someone can help you when service is needed, it should last a few more years.
Also, it would be best to use it as Grandpa did, if you start adding mods and offroading, expect breakdowns.
denton county, tx