Big job...depends on whether you can do it yourself or not?
You can get conversion parts to go to a front mounted pump...probably $500 in parts alone at least, probably $1000 best case for the whole job. The timing case needs to come off, that may involve removing the head or sump or both which will be the varying cost for labour, it might even cost a couple of $grand if its head and sump off.
Cheers,
Phil.