Whether it's a good trade or not probably depends on three things:
The biggest is Walker's health. If he plays every day, you'll do well here; if he goes through a spell of nagging injuries once again, you'll be left with a huge hole.
Also, it depends on your current options at 1b. If your current starter is solid and you either already have a viable backup or there are some potentially useful players on the wire, trading for Lee might not be worth it.
Finally, it also hinges on who you would be dropping to make room for Lee.
It basically all comes down to Walker's health, though, and that's one thing that can't be predicted accurately. If your team is struggling and you could use a boost, this trade might not be a bad risk to take. If you're already among the leaders, however, playing safe and staying put is probably the better path to follow.