If you are prepared for some reading then look up www.sustainabledressage.net
There are a lot of valuable helpful hints. Some info might be a bit advanced for a newcomer to English riding but the tack you need for the swop over is well discussed.
The biggest difference between Western & English lies in the cut of the saddle, the way you use the stirrups and the way you hold the reins. Eventually after lots and lots of practice - the horse will come to ride in a rounded outline
And the rider will hold the reins in such a way as to have permanent contact with the horses mouth.
But doing it all on you own without someone nagging from the middle of the arena will be a tough long haul.
But best of luck and enjoy.