My lint filter slides in from the top of the unit. To open the top of the dryer, I pull the lint filter out and remove the 2 screws that hold the lint filter duct to the top of the dryer. Once those screws are removed the top can be opened for full access to upper portion of the inside of the dryer.
I also remove the back, which gives me access to the rest of the inside, including the screws that hold the lint filter duct over the blower housing. Once those screws are removed, the entire inside of the dryer can be cleaned.
Do you use dryer sheets? If so, you should wash your lint filter with warm soapy water every few months. Dryer sheets cause a waxy substance to build up on the lint filter which inhibits air flow. Try to run some water through your lint filter. If it holds water, it's clogged and should be washed.