Hi there.
It is normal to find more resistance when turning, as these machines dont have a differential, so one wheel has to slip when you turn.
Cutting blades traditionally fitted to all early ride ons are usually 1 pair of flat blades and one pair of fluted (bent up) blades.
Wheels on the deck as bruce has said are the standard 6" rover type, fitted to the front of all their early push mowers.
Tubes & tyres are as bruce posted 2.50-6, you want bent stem tubes, I would recommend leaving the original tyres as they look better than the modern ones, unless they are really bad. You should find tubes at any mower shop.
I have only ever used just plain old grease in all my foote gearboxes, biggest problem is they were never designed to hold oil, so you will find if you use a liquid based lube it will gradually leak out. this also means if you wash it a bit too thoroughly water will get into them and ruin you're grease. They aren't exactly a state of art piece of engineering like a car gearbox. Just make sure you put plenty onto the bearings as you assemble it, and I generally just pack as much as you can into and around the gears as you put it together.
