Seems like a good find. Do you have service records from the previous owner?
If you don't have records or it hasn't been changed in the last 50k miles, the first thing I would do is change the transmission fluid. That is the first thing to do when you experience any shifting issues. Blow the money and get a full flush from the dealer. Including filter if equipped. I'm not familiar with that car so give specifics on fluid type, etc. You could suction out some tranny fluid and run some ARx for 1000 miles in the transmission before the flush. I highly recommend Lube Guard red bottle transmission addative with the transmission flush.
For oil, as long as you use something that meets the required spec you should be fine as long as your oil change intervals are reasonable (typically 5k for conventional and 7.5k for synthetic). If you can see through the fill hole and it doesn't seem gunked then no need for ARx, Kreen, MMO, etc. If you don't see anything through the fill hold, but want to do some cleaning anyway just to make yourself feel better, run PU or Redline through it for a couple 4-5k mile oil change intervals. The Kendall won't be quite as good at cleaning as these other two, but at a price like that I'd go for it. It is a good oil.
If you don't have records and/or they haven't been changed recently, you should also get the coolant, brake fluid, and power steering fluid changed.