Also, converting any old modules would seem to automatically make them 2 levels higher, so that a 1st level B/X module should be a 3rd level module in 5e. I don't want to start the game at 3rd level, but that seems to be what the ruleset expects. In general, 5e seems to have seriously amped up monster hit dice and special abilities. Goblins have up to 12 hp and +4 to hit, and get an extra action every turn to Hide. Kobolds have up to 10 hp and get +4 to hit.
Specifically, all the standard goblin-type threats look pretty dangerous in 5e. I'm now going to be DMing 5th edition, and I need some help on encounter design.