Changing the rad isn't that much of a hassle wink ;
First remove the front grille, held in place by a couple of bolts on the top, and at the bottom, beneath the headlights its held in place by a couple of plastic retainers, gently pry it of. This should give you access to the two bolts that holds the top of the rad in place. I'm not sure about this, as its been a long time since I saw the engine bay of a 146. But maybe you also have to remove the radiator support beam fitted below the radiator. Having done so, remove the thermocontact connector ( might not be fitted to your car), then remove the collar of the lower hose, yank of the hose and empty the coolant into a container. Measure the amount of coolant, as you need this figure in order to keep track of fluid let out, and fluid replenished. Then remove the upper hose collar and remove the rad. Fitting is the opposite of the dismantling procedure. When it comes to adding new coolant, You might experience a problem with getting in as much coolant as you let out in the first place. Keep the engine running, squeeze the hoses and replenish. Then take it for a spin, keeping an eye on the temp gauge. And over the next few days, monitor the coolant level in the header tank.
As for the excessive tyre wear, if both front wheels have the same amount of wear, the lefthandside maybe a little more, then the tracking is the culprit here. But if the XS wear is limited to only one wheel, something is really wrong. Consider having a four wheel alignment done. Feel free to email me with the results before the workshop start to drain your wallet
I dunno if you had the wheels balanced, but the workshop are right, this cures the wobble, unless the rims or tyres are badly damaged.
All the best