i have 82 dodge slant 6/225 i have to replace the one way valve on the exhaust pipe that come from the smog/air pump it looks like the original unit. i need tips on how to break that bolt loose with damage to the pipe itself thanks

I bought a 2000 F150 XL V6 5 speed last fall and shifting into first and sometimes second has always felt a little tight. The clutch pedal has 3-4 inches of play and when I took it to a mechanic 6 months ago, he said it was fine and didn't need anything. I also think he was in a hurry and couldn't work me in to look thoroughly. This shifting problem comes and goes, but has recently become very difficult. Today, I have driven it 3 times in 3 hours and the 1st time it was fine, the second almost impossible to get into gear, and the 3rd time was fine again. Any idea what is going on? There is plenty of clutch fluid. Are there any adjustments I can make. I can probably make repairs myself if it doesn't involve pulling the transmission.