Here are some helpful points when looking for "estimates" on liner installations.
First, how did you get to the point of knowing you needed a liner? Many times there are visual clues to necessitate chimney lining. That being said, it is important that a Level II inspection be performed prior to relining. The NFPA 211 (the minimum national standard for chimney professionals) states the following under the circumstances of a level II inspections:
"Upon addition or removal of one or more connected appliances or replacement of appliance with one of dissimilar type, input rating, or efficiency; prior to relining or replacement of flue lining; upon sale or transfer of the property; after operating malfunction or external event likely to have caused damage to the chimney. "
Second, there can be other extenuating circumstances regarding the chimneys construction, condition or past alterations, that may make relining difficult. It is better to know these things in order to better plan for the proper job.
Finally, flue sizing is vital to the operation of all chimney and vented appliances. A Level II helps ensure proper sizing is possible and the path needed to create proper sizing, get permits and perform proper relinings.