You need to be concerned with the NVRAM chips - DS1486 clock chip and the DS1650/DS1250. They have internal batteries that hold the calibration constants and options info. The batteries expiration date ended many years ago. So, if those chips haven't been changed, you need to attend to it. Many articles on backing those chips up using the GPIB interface, the internal disk drive, and other ways on this site and forum.tek.com. But, hopefully, someone swapped out the chips already.
Great scope - good luck, with it! I have a TDS754C.