looking for a solution to migrate from bloghoster to WPMU

Hello fellow WPMU’ers since five years i use Bloghoster, since that system is not maintained for quite a while i would switch to WPMU, but like always there are some issues.

1 – i have over 10.000 posts in BH.

2 – I have over 600 Users.

3 – i have 20 GB of data (images and other files)

So i need to have some help, is there any conversion script out there to do the migration job for me.

// Peter