To me, it seems like you already have it figured out.
I have some tapes from the sixties that I've converted to digital. But since I was converting music, my standards were a lot higher. For voice, you don't need to be so demanding. There isn't likely to be any content going up to 20kHz or down to 20Hz.
The first thing you need to know is the tape-speed. Music was typically recorded at 7 1/2 ips, and sometimes 3 3/4 ips. Voice could either be 1 7/8 or 3 3/4 ips. High-end decks could do 15 ips. Because the head-gap was specific to the tape-speed, most decks only had a two-to-one speed range:
15 and 7 1/2 ips (pro-decks), or
7 1/2 and 3 3/4 ips typical decks for music), or
3 3/4 and 1 7/8 ips (for dictation).
Most decks you are likely to find are in that middle range, and your tapes are likely 3 3/4 ips. But you need to verify the speed before you get the wrong deck.
Mono verses stereo won't matter, as the mono track is twice as wide as the stereo track, and therefore plays on both left and right channels. Keep in mind that both mono and stereo tapes had two sides, and you will need to flip it over. You likely know that already, but I bring it up because it isn't obvious.
The input to your computer is pretty straightforward. For software, I use Kristal Audio Engine
, but you can get away with something simpler. I would record at 24-bit / 48 kHz, which should be the most compatible and still have more than enough resolution for your needs. 16-bits should probably be enough, but 24-bits would give you the extra dynamic range in case you wanted to boost very quiet passages. And once you're done processing, you could down-convert to 16-bits, or even 44.1 kHz if you wanted to put your final results on audio CDs.