( for my real job) i estimate construction costs, mostly large commercial and public projects.
I would say I am careful about what I break out because it opens me up for possible items that I didn't anticipate ( allot of costs are dependent on others in a contractors mind). there are allot of spread costs that when bidding, you are high on some and low on others but in the end you hope it will even out and end up with the profit margin you anticipate.
as for the comment of saving 30k by managing yourself? i highly doubt that, unless your scope of work is truly small and you are hiring a contractor that literally doesn't self perform any work, which in this world the competition is too fierce, and a small time reno contractor wouldnt stay in business too long if they are just simply "pushing paper".
@Scott C. is exactly right. With large contracts there is always a set of plans and a set of specifications detailing exactly what the client is expecting, all the way down to the grade of nail to use for each item.
On my rehabs I hire the trade contractors directly, there is less risk because if i mess up then i just have to repay/negotiate with that sub on the work, if there is a general contractor in the mix then im paying the sub to redo the work plus the general's profit overhead, again.
I make up a simple scope of work, with line items for each general scope ( example: painting whole house scrape prime plus 2 coats, all drywall work for bedroom #1, all electrical for kitchen, etc,) they dont have to be extremely detailed, but enough detail to allow you to pay the contractor in regularly billings for percentages of work completed per scope and actually be able to explain to your boss ( i always say i have a boss just to end that discussion, be it my wife or my dog or whatever).
I usually have a simple paragraph stating the exact types of materials I want used and reference that all work must be in accordance to the latest applicable IRC. In there I state that They must have me inspect their work at individual milestones for pay ( example: painting the house I must inspect after scraping to ensure enough scraping was done and prior to 1st coat, inspect again prior to second coat to ensure I really did get a good true first coat of paint, etc.)
I also base pay off percentage of work complete for each line item. you both must agree to the percentage at time of pay. up front on the contract I state that I hold a 10% retainage from all billings to be paid upon final satisfactory completion.
regardless of the area you are in ( the company i work for, i bid work in every state) it is acceptable for you to utilize the basics of contracting including detailing out a scope of work, paying based on percentages of individual milestones, holding retainage to ensure satasfactory completion.
now some small time contractors may be unwilling to work with you because its obvious the standard you will hold them to and they wont be as easily able to half *** their way through the work and blame you for not being specific. but most will, and may even prefer it as long as this is discussed and detailed in the executed contract. Another item i do is I use my own contracts which is very common with larger value projects ( owner to provide the contract) but less common with small 100k or less type contractors, most dont have a problem with it and it allows me to just throw my scope of work into it as an appendix and all my requirements about retainage and inspections and IRC references is in there.
as far as your 95k bid goes. get 4 or 5 more bids, it will become obvious where the fair value is. I enjoy getting allot of bids, and its very simple once you have the scope of work, line items written up. simply meet the contractor at the house give them the piece of paper and continue.