Just a addon to Mr Simpeltons reply. The 2465A and B use the same hybrids. The 2465b with a serial OVER bx50000 will use a SMD logic board (A5) which is not a issue except there is 4 SMD caps that are known to leak. If leaked they could have damaged the board.
If I am correct the 2465A may also uses a Dallas Nvram like the 2465b to store settings and calibration data and you will need to eventually have to replace or risk losing your calibration data. Only have a recommended life expectancy of 10-15 years. You will need a programmer to swap the settings between the old and new module or recalibrate from scratch.
The 2465b requires specialized equipment to calibrate properly, not a easy task.
Honestly unless you want the "TEST" button on the 2465b a 2465A or even a 2465 will do you well. I find the parametric measurements are not really that accurate and you would normally use other equipment to test. Most of the measurements are around 1-3% accuracy. A simple DMM of today can do better. this is where the Rigol is better IMHO. All models have cursors
Whatever you decide your first task will be to recap the power supply, the caps are known to leak, many of the "dead" 2465 scopes on the market are often nothing more than a defective power supply. lots of help available on recapping the supply. Easy peasy as they say.