Errors upgrading from 1.7.1: unable to load class, forum error

Got most of the way through an upgrade from 1.7.1 to 2.10.1, but encountered two errors at the end that I’m stumped over:

Trying to get to the control panel, I get:

Unable to load the requested class: view

Then when trying to go to our home page, I get a syntax error for the forum tags in my templates

The following has a syntax error:
{exp:forum_forum_replies}

. I gather these tags have changed, and that probably won’t be the only tag that trips us up. Is there a good guide to updating these?