Um.....having lived with a chimney sweep as my roommate, I can tell you that it's highly likely they'll tell you you have to clean the flue before you inspect it. Sorta hard to see damages through the creosote, ya know?? :hmm:
All the masons I know would be surprised to hear that. They regularly check for failed mortar and broken brick on uncleaned chimney flues. Why would anyone pay extra money to clean a flue that needs to be relined?
$140 seems high to me. Have you called around at all, OP? Also, do you know if it's a metal or clay flue? If it's an clay "pipe" flue, I'd have a professional do the cleaning & inspection at least once, before you even think about doing it yourself. They will be able to tell you if you have any broken flue pieces, or missing mortar in the joints between the sections.
Chimney sweeps are not masons. They may be able to spot obvious problems but are unqualified to asses how much damage or repair is needed. Again why would you spend extra money to have an unqualified person inspect it?
They can also inspect the firebox and damper areas, and assess the condition of your chimney cap, if you have one (and can sell one to you if you need one, plus install it for a nominal fee). Make certain your chimney sweep is certified by the National Chimney Sweep Guild (they require a written exam to be passed, I believe by 80%, before they certify a sweep.....no small feat, as I've seen the study material my old roommate had to study in order to pass his test).
If you have a steel "pipe" flue (actually, a pipe within a pipe, with insulation in between the two), you might feel comfortable enough to sweep it and inspect it yourself. That's up to you. Personally, I'd still have a chimney sweep come out every few years, just for a professional job.
As far as sweeping the flue goes, there's different sizes of both varieties, so you'll have to figure out what size it is, then go buy the brush and rods (think they come in 8' sections, but don't quote me on that.....it's been almost 20 years now!). Close the damper, and put a HEAVY canvas tarp over the opening of the fireplace, with the suction hose of a heavy duty shop vacuum (with a clean HEPA filter) in the firebox area of the fireplace while you're sweeping everything down from the top of the chimney. This is going to keep you from having to clean the remainder of your house when you find out you had fine soot come out of your fireplace while you swept it down the flue pipe! Once you've got it all swept down, you can go into the fireplace, again with the vacuum running BEFORE you start doing this, and CAREFULLY open the damper, SLOWLY, so as to vacuum up the soot before it gets past you. Finally, take a long-handled wire brush and brush out the soot from the damper/firebox area, while holding the vacuum cleaner hose right beside where you're brushing, so as to catch the soot you're cleaning off the metal/brick areas. Oh yeah, and make sure your vacuum is a big honking one, not one of those little 2 or 3 gallon mini wet/dry vacs. Believe me, if your system is dirty, you'll be amazed by how much soot you'll sweep down!! Replace your HEPA filter once you're done (trust me, it'll be FILTHY).
Chimney sweeping is dirty, difficult work......and that's on a good day! Now you know why they charge so much! Oh yeah, and if you have a fireplace insert, be prepared to either have a couple friends help you with it, or be a damn weightlifter yourself, cuz them suckers can weigh a couple hundred pounds, easy, and they're usually fitted pretty tightly in the fireplace firebox. Better yet, pay the chimney sweep to deal with it........you'll be glad you did, once you see him having to pull it out and push it back in!!