Luckily for me we have an island in front of the fridge. I disconnected the propane and all the power thru the lower vent. On a rig where the frig is not in a slide you will only have one vent but the access you need will be inside that.
From the inside I removed all the fasteners and tilted the fridge over onto the old coverlet padded island giving me access to the fan. I replaced the single fan with 2 of the same size by rigging a dual harness and using the existing mounting ridge. I got the fans from amazon (Wathai 9225 92mm x 25mm 12V 2Pin Dual Ball Bearing DC Brushless Cooling case Fan (Computers & Accessories) which were the exact same size and you can barely hear them outside. The replacement reason was that the original 6 year old fan still worked but had become very noisy.
Without the slide to lean the frig on you can use an old table to slide it out on or get a friend to help you set it on the floor. They are not that heavy but unless you have 6 foot arms it's not a one person job.
Reverse the process but make very sure that the propane connection is leak free going back. Keep the frig as upright as you can as you work or don't turn it on afterwards for a day or so if it's an absorption fridge.
On edit Make sure you verify fan air flow direction before you button it up.