Taxis are spendy (unless you’re on a corporate expense account). The subway system is extremely convenient, however, so you should be able to get around pretty easily, and most station workers will speak enough English to help you on your way.
From Shinjuku Station, Ginza is 8 stops (about 16-18 minutes) on the Toei Marunouchi Line (the red line on the subway maps), going towards Ikebukuro.
Tokyo Station is one more stop, and Tokyo Station is pretty cool.
I’ve lived in Japan on and off the late 80s. Last time I was there, I actually lived in Ginza (technically Shiodome). My apartment overlooked the Hamarikyu Gardens. This is a beautiful public garden - do a Google Images search. Might be a bit tricky to get to, so I’d just hop in a cap from Tokyo Station.
Tsukiji is close by as well, and it’s quite cool - it’s walkable from Hamarikyu. Unfortunately I am pretty sure the market is closed on Sundays.
November would probably be a good time to go to the Meiji Jingu Gaien Gingko Festival. Street performers and such along the avenue of gingko trees; when the weather is nice it’s beautiful. I believe it’s a 5-10 minute walk from Aoyama Itchome Station (three stops on the Marunouchi Line going towards Ikebukuro).
Meiji Jingu means Meiji Shrine, and it’s also beautiful in its own right; definitely worth a stop if you have time. It’s a short walk from Harajuku Station (also a cool spot to walk around for people-gazing). Harajuku is just two stops from Shinjuku on the JR Yamanote Line going towards Shibuya.
Asakusa Templeis fantastic. It’s about 30 minutes by train from Shinjuku: Take the JR Chuo Line towards Tokyo, 3 stations, and change at Kanda Station to the Toei Ginza Line, six stops to Asakusa (last stop). You can of course go directly from Ginza; 10 stations on the Toei Ginza line towards Asakusa.
One idea is to hit Asakusa in the morning, then work your way back through Ginza in the afternoon and hit Meiji Jingu Gaien and the gingko trees in the early evening?
Tokyo weather in mid-November will be a tad on the cool side during the day if it’s sunny - high 60s maybe? - but can sometimes dip in to the 40’s in the evenings. You’ll probably want a jacket or something.
If you’re into electronics and maid cafes and the like: Akihabara. 20 minutes or so from Shinjuku, either 9 stations on the Chuo-Sobu Line towards Chiba, or 14 stations on the Yamanote Line towards Ikebukuro.
If you’re in the Ginza area on a weekday night looking for some dinner and drinks, Andy’s (Shin HInomoto) is an institution for foreigners and Japanese alike. I personally have been going here for 20 years - almost as long as Andy’s been working there.