Some McCulloch MAC chainsaw manuals can be found online at http://lawnandgarden.manualsonline.com/manuals/mfg/mcculloch/mcculloch_chainsaw_product_list.html. The 3516 manual specifically is located at http://lawnandgarden.manualsonline.com/manuals/mfg/mcculloch/mcc3516f.html. These manuals are not free to download and it will be necessary to pay for them. They can be sent in paper form in the post or as a PDF by email. A part list can be found online at http://www.oscar-wilson.com/MANUALS/MCCULLOCH/211318-03.PDF that will provide the information necessary when dealing with a specific part of the chainsaw that needs repairing.
The support section of the McCulloch website (http://www.mcculloch.biz/int/support/) also offers a range of advice and information about repairing chainsaws. Repairing a chainsaw can be a difficult and dangerous task that should only be attempted if you are fully prepared and confident with the work you are going to carry out. Most manufacturers will offer an option to send tools off for repairs at a cost so it is worth researching how difficult the specific repair is. The customer service helpline for McCulloch may offer over the phone advice. This way the telephone advisor may be able to help you with your repair over the phone. Using this method you will be able to ask questions about your unique question that are unlikely to be listed in a general repair manual. Once you have discovered the exact problem, you will then be able to determine whether it is something that you can attempt yourself reasonably easily or whether you will need to seek the help of a professional. Attempting to repair the chainsaw yourself does have a possible consequence of it going wrong. Should this happen, any warranty you may have could become invalid and the cost to repair the extra damage may be more than getting it fixed by a professional originally. Use the websites given above to try and distinguish what repairs need to be carried out on your chainsaw before tampering with it.