Allow a couple of hours to achieve a decent job. Above all don’t be tempted to rush. You will find it hard to live with any imperfections you could have avoided by doing a proper job.
Expect to pay around £50 for a new seat cover. Decent value given the standard to which many of the aftermarket ones are produced. The TS one here features stitched-in beading and perfect reproductions of the ‘Suzuki’ and ‘ER’ legends on the vinyl.