Thanks for all the answers so far!

I'm not sure which terminal I'm arriving at since I can't find it anywhere on the ticket. But I'm flying with China Eastern Airlines from Beijing, so maybe you know?

I think the Keisei Main Line or the Sky Access Line sounds like the best options for me going from the airport to the city. It's cheap and I don't mind using 80 min instead of 50 min. From wikitravel it sounds like I should use the Sky access Line on the evening (When I arrive at Monday) and the Keisei Main Line in the morning (When I leave at Friday). Is that right? And when should I take the train at Friday morning to be sure to reach the plane? It's leaving at 10:55 am and I'm probably only going to have a carry on. And btw. do they speak good English at the airport in Tokyo and in Beijing?

As for the hotel, I'll drop the thought about capsule hotel. It would be a cool experience for a night, but obviously not a place you stay for several days. I want a single room as cheap as possible close to the ueno station. From there it seems easy to get to the airport and to get around the city with subway! I was thinking for example something like Chisun Hotel Ueno or Ueno Terminal Hotel for around 20,000 yen from Monday-Friday. I'm not picky about the standard.

I'm arriving in early June. I'll check up your suggestions so far.