[Riee]

>How easy is it to buy japanese series and films with english subs?
Series with english subs? Usually they never get subbed...
Nevertheless if you still want to buy some, than just look for example at a Tsutaya-Shop (in Shibuya in the same building as the Starbucks that you will see when you exit the station on the hachikou-side). Also the big department stores (Seibu, Tobu) often sell them, same as some CD-Shops like Tower Records or HMV. For 2nd Hand DVDs I'd advice you to go to Book OFF (one of the biggest Book OFF stores is in Harajuku).

>Is there any site on the net for looking up japanese events online? Like concerts. A site with artists, genres and access to book tickets?
Yes there is, but it is usually only written in Japanese...
But in general you can't book them when you're overseas.

>If you got to visit osaka, kyoto, tokyo and sapporo. What would you do and why?
It just depends on what you're interested in...

>We're suckers for the clothing style called "Lolita". Does anyone have any tip or hints for this?
There are some shops in Harajuku, for example on the B1.5Floor of the Department store "la fôret" in Harajuku, others are just single shops located sperated in the streets. Especially on weekends you can also see many Lolitas walking around in this part of Tokyo.
There's also one 0I0I-store in Shinjuku which should have a Floor where "Lolita"-Clothes are sold.