I change them myself. I break the bead in a 6" vice then put a section of slit hose round the rim to protect it along with loads of washing up liquid round the bead. Two tyre levers and just work it round until they are off. It can be a bit of work on the semi on/off road tyres as they have harder side walls but you shouldnt have to use too much force. If you are having to push the levers hard then your taking too much of a bite. Release the lever and move closer to where it is already off and try again. Once off, fitting it is the reverse, loads of liquid again and the first side usually goes on without even using levers. If you need levers then put the bit hose on again and lever it on with small bites. Once you have it all on. Make sure you get the direction arrows the right way round and check that the red dot on the side wall is at the valve. Keep the valve core out for initial inflating so the air goes in quicker and turn the pressure up on the airline. The whole idea is to get as much air in as quickly as poss so the bead pops. You will never get this done with a petrol station compressor as they dont have stored air usually. Anyway if air is leaking and it wont pop then turn and bounce the wheel a few times then put the wheel upright against a wall and press your knee against it so you have pressure on three points (floor, wall and knee) and put the air in. If it is still not working then kinda bounce on the tyre a bit with your knee. You will hear the leak stop and it will seal itself and pop. if it is a really stubborn tyre then get a bit rope and put it round the centre of the tyre like a tourniquet and tighten it. After its popped then put the valve core back in and inflate to your pressure, job done, go for a ride or have a beer. Takes about 10 mins a wheel 20 including wheels on and off and is even easier if you can get a mate to lend a hand. I have been doing my tyres this way for 25 years and have never had to balance one yet unless it was out of balance before. Tyres shouldnt need balancing (this is what the red dot is for), its the wheels that need it, especially if they have been damaged. If there are weights on the wheel already then leave them on and everything will probably be good.
