No sweat if you have all the right braze-ons and eyelets, just nuts and bolts for all of those. A 5- or 6mm Allen wrench and 5-mm box wrench will get the fenders and rack installed. Fenders first: the SKSs are not hard but take some time to adjust. Then add the rack.

The pedals are a bit trickier. Having a real 15mm flat wrench makes a big difference. I've done it with adjustable wrenches before, but be careful. Remember that pedals are threaded different directions - always turn the wrench towards the back of the bike to loosen on either side.

Be prepared for a full night of installing, removing, adjusting, and possibly cursing.

BTW, this is a good topic for the bike maintenance forum.