I would suggest having a look at the FAQ section at Audio Asylum. If you have any doubt that the stylus is in good condition with minimal wear, get a replacement before you start. Something like the Audio Technica AT95E should be fine. You might also be able to find a replacement stylus for the current cartridge. AT also makes a decent inexpensive phono preamp called the AT-PEQ3.

The hard part is aligning the cartridge and the tracking angle. The arm might have no adjustment for tracking angle, so you would often have to live with whatever you have in that regard. The top surface of the cartridge should be absolutely level if possible. Without arm adjustments, sometimes the tracking angle can be suitably corrected with a different mat thickness.

For cartridge alignment, you should probably find a protractor, such as those available for download at Vinyl Engine. If you have reason to believe the original cartridge was installed correctly, with some degree of expertise, you could document the horizontal distance from the back of the headshell to the stylus and repeat that distance when you install the new cartridge. If you can't replicate the horizontal distance that the tonearm was designed to, you might have to angle the cartridge in the headshell to align the cartridge to a protractor. If that happens, it is acceptable and will sound fine.

Regarding tracking force...set it to what the cartridge manufacturer recommends, but then adjust by ear to your liking. They often track better with a little extra force. The markings on the headshell are often not very accurate, so I'd say get a small scale to measure the force if you don't feel confident adjusting by ear but want it accurate. Possibly contrary to intuition, a little extra tracking force will not harm your records. Too little force will.