My experience with this firm was terrible:
they didnt complete all the work in the contract
they damaged my neighbors property and left me to repair/replace it
the work was sloppy and unprofessional
when the work leaked they blamed others and refused to repair it
I have moved on to more professional firms, and I suggest you do the same.
Pros: cheap
Cons: sloppy work, guarantee is meaningless, damage to adjacent properties
more