Outdoor antennas are almost always better than indoor antennas in normal circumstances. But as has been noted, installing them is much more complicated and expensive than lashing up the simple wire version of the OCFD shown in the RR Antenna Wiki. Will it be better than a top-of-set antenna on your Pro-107? Absolutely, particularly if you put it on the upper floor or attic of the building. Will it be better than an outdoor antenna? Very likely NO. Outdoor is best, But the wire version of the OCFD is about $10 and 15 minutes of your time to rig up. And no worries about grounding, getting to the roof, etc. For the time and energy you'll spend it's worth it in the likely improvement in signals you'll receive. Quick and easy... and you can do the outdoor antenna later in better weather, more time, more money, etc.
It will be negatively affected (as is any indoor antenna) by large metal objects (HVAC ducts, metal roof, etc.) and wiring or aluminum foil-backed insulation in outer walls. So put it in a window if you can (hopefully one that it is not tinted or has metal particles in the glass).
Outside of the building taped to a wall MIGHT work, but very sketchy if you have wire in the walls. And absolutely useless with aluminum siding.
The 75 to 300 ohm transformer is the same thing as a 300 to 75 ohm transformer. They are standard TV-type transformers with two wire leads that go to the OCFD antenna elements (300 ohm side) and an F-female connector on the 75 ohm side, where you will attach standard RG6 TV antenna cable. Put the antenna as high as you can in the building. With VHF/UHF height is king and trumps other considerations.
