If he is purchasing an air nailer, he will require a compressor. Most of the brand name tools found at your local home improvement stores are good.
A hammer drill would be the right tool for your use. It's very easy to use no experience needed. Yes you can rent one.
An impact driver and a rotary hammer are two different tools. For your application, you would need rotary hammer drill. We would recommend either Bosch or Dewalt, and one that is rated between 3/4" to 7/8". The price range will be in the $250-350 range. An impact driver is for fastening, and the impact is lateral to create torque, and not meant to be a percussive tool to make holes in concrete. The main application for this tool is putting screws in wood or metal. This tool will not work in making holes in concrete. Once the anchor holes are made, then an impact driver can be used to fasten the anchors in.
Most professionals use compound mitre saws to make accurate cuts for crown moldings. Depending on the size of moldings you are cutting, typically the smaller the saw blade, the more accurate the cut. This is because the larger the blade, and the more aggressive the angle of cut, there is a slight flex in the blade. One popular size of mitre saw for cutting only moldings is the Makita LS0714, which has a 7 1/4" blade and is a sliding saw. As well, the Hitachi mitre saws have a digital read-out for the bevel and angle so as to have accurate cuts.
You can replace a sliding door with a French door. Tools are going to depend on what brand of door it is as each company has its own installation instructions that can vary. If it is a Pella unit, the Lowes should be able to print you out installation instructions for the particular unit you are purchasing. Those instructions also come attached to the unit. As far as tool wise, depending on what is purchased with the door itself (i.e. nailing flange, extension jambs...) will determine what tools are needed.
There is a tool that looks like a hook and has a carbide tip. These typically have a yellow handle and are available at most hardware stores. With this tool you can scrape out half of the grout and then re-grout over top. Use a darker color than you previously did to avoid it darkening which is inherent for grout. You can then seal the grout to give it extra protection, but sealing is only possible after the new grout has set for a minimum of 72 hours.
Yes you can soften the tile with a heat gun but you must be very careful it isn't too hot or you get too close to ignite the glue. The element must never touch the tile. Have fire prevention measures at hand. Depending on the age of the tile there should be no asbestos used in the tile.
Your choice should be based on the intended use of your saw and your budget. However the short answer is for most craft projects a jigsaw (good one) will do a lot of cutting for you. Visit the library and check out their hobby section you will find invaluable help and see things you may want to make and the best (saws) tools to use
As far as we can find there is no instrument made to solve this problem. You'll have to locate one stud where you know for sure it is and measure from there.
You will need a proper sanding machine if you want a job that you will be happy with. Perhaps you can have someone do the sanding for you and you do the refinishing. The rental companies that supply the sander might be able to help you.