Yes you can replace the screen but the cost of replacement would probably be more than the phone is worth I see on ebay the going rate is 125 for a replacement and you will need a complete replacement LCD digitizer and glass complete .
http://www.ebay.ca/sch/i.html?_odkw=Samsung+Galaxy+S+II+Plus+screen&_osacat=0&_from=R40&_trksid=p2045573.m570.l1313.TR0.TRC0.H0.XSamsung+Galaxy+S+II+Plus+lcd.TRS0&_nkw=Samsung+Galaxy+S+II+Plus+lcd&_sacat=0
this is a tear down video for your phone
https://www.youtube.com/watch?v=pDkvz9fUgNI
Everything can be fixed but not everything should be . If you have important data on the phone even with a broken screen you should be able to connect and retrieve the info unless your phone is password locked
Hope this helps