yeah, I've got cord changes down pretty well, having played accoustic for 30yrs or so, can bang out some decent songs, I'm no good with leads, tho i know the scales somewhat, I just need to get better at the intricacies like all the myriad cord variations, changing keys, diff.strums and all the cool techniques better players use, hammering, muting, harmonics, shit like that...and just knowing how all those knobs/switches can make my guitar sound like I want...yeah, I know...it's a journey...and it's damn fun, too!!!
You've definitely come to the right place here. Sounds aren't hard to get. For a player like yourself, primarily rhythm guitarist, knock the mids down on the amp. Play with the bass and treble at 12 or 3 o'clock and the mids on about 9 o'clock. If there is a master volume and a gain or "drive" volume, boost the gain or drive volume and turn the master volume to whatever volume you want. That will make distortion. Reduce the gain or drive volume and increase the master volume. That will make a clean sound. The difference between a rhythmn and lead sound is mids mostly. Turn the mids up to play a lead.
As for the guitar, just play with the volume up all the way. Play with the 5-way switch in the second to rightmost position. That will engage the middle and rear pickups together and makes for a nice traditional strat sound that's suitable for most things. Go all the way right and you've got just the rear pickup and it will be more bright and trebley. That's good for lead work with distortion from the amp, and also good for country sounds when clean. Put the 5-way switch all the way to the leftmost position, and bring your tone down on the guitar, volume up. With distortion, that will give you a bluesy sound, called "woman tone". Give those things a try. Write down the numbers/knob positions when you've got a sound you want to remember how to get. Eventually it's all second nature.