If you are seller, your best bet is to have new buyer enter into a brand new lease. This benefits the seller two ways. One , that all liabilites are released, including personal guarentee, and second, the new lease has nothing to do with previous lease.
If your a buyer, you should try your best to assume the lease. This will allow you, as a buyer a protection under the old lease, in case if you decide to bail out during the lease terms, the seller will still be assume under the personal guarantee. Hence, will allow you double protection.
This may contradict it's self, but these are two point of positive view that buyer and seller should consider.