You got lucky if you were able to cut all the sealant with a putty knife. I've had cars with so much sealant I couldn't easily get at the bolts on the a-pillar even knowing where they were.
Another problem is sometimes there's so much sealant under the front lip of the fender that you can't reach it all (I've seen it an inch thick), and forcing the fender at all will bend it. In that case I could only think of one thing and it worked:
Torch the sealant until it lights on fire and wait for it to burn up . After the fender was off, abundant cleanup to remove the evidence...
You can choose to leave the fender if you live in Arizona and/or you're confident you have a rust free mk1.