I know that buying and installing RAM from a regular computer shop will be cheaper for me. I was just wondering if a Macbook Pro 17" early 2011 model uses specific 'Mac' DDR3 RAM or if I can get away with any DDR3 RAM?
Generally in principle yes. You do not need to purchase expensive Apple memory.
However you will need to check for each model - the best thing is to go to a reputable memory supply company website which sells certified RAM and look up your model.
You can search for them online but here is a respected store (I have no affiliations with)
Just be sure the memory you buy meets the specifications on Apple's website.
It's a very common type of memory, 204-pin PC3-10600 DDR3 1333 MHz.
Although memory chips conform to standards, there could be some minor variations. So it is advisable to buy from a seller who tests and guarantees compatibility of the RAM sticks for your Mac.
Two such stores in the U.S. that have served customers for a long time are OWC - MacBook Pro 2011 RAM and Data Memory Systems - MacBook Pro RAM. These are usually cheaper than Crucial and offer good warranties.