I just did this job a couple months back on my 300E. Take a Dremel tool and carefully grind off the stakes. Don't nick the bore while grinding otherwise you'll have a tough time pressing in the new bearing. The bore must be smooth. If you do nick it, dress it down with the Dremel so it is smooth again. Once the stakes are ground out, use a socket to knock out the old bearing.

As DG said, use a socket to press in the new one, pressing ONLY on the outer race of the new bearing. Do not press on the inner race - it will destroy the bearing. There is an exact fit el cheapo socket for this job. I got it at AutoZone and I mean it is an exact fit, like it was made for the job. It is a Great Neck el cheapo socket - I think the size is 2" or 2-1/16" or something like that - I will get it if you need it, but just take the bearing to AutoZone and find a socket that exactly matches the diameter of the outer race of the bearing.

Then place the bearing in the freezer and the pulley in the oven, again as DC said. Stick the bearing in the freezer the night before you do the job. I used red Loctite to set the bearing in place - that might have been overkill. It was a mess, trying to handle the cold bearing, hot pulley, and the Loctite all at the same time. Put the pulley in a vise while doing this or get a helper and the job is much easier. Good luck!