First off, for learning I would suggest getting a dead receiver, preferably a mystery repair with at least one busted output stage (you can search ebay on vintage audio for "parts or repair").

Make it your mission to fix this. You will probably eat through a bunch of parts and it will be frustrating - but this is the best kind of learning you can get. Reading won't substitute for doing.

This site is invaluable:

http://sound.westhost.com/articles.htm

Particularly these pages:

http://sound.westhost.com/troubleshooting.htm

http://sound.westhost.com/articles/troubleshoot2.htm

http://sound.westhost.com/miscc.htm

Also recommend reading all of these:

http://www.repairfaq.org/sam/tshoot.htm

http://www.repairfaq.org/sam/audiofaq.htm

Go here for service manuals:

http://elektrotanya.com/

http://www.hifiengine.com/

Go here for advice:

/r/audiorepair

http://www.audiokarma.org/forums/

/r/askelectronics

Tools and supplies (in no particular order):

Good multimeter

Flush wire cutters

Screwdriver set with multiple heads - including torx

Pliers

Solder - leaded

Rosin Flux

Good solder station - Hakko 888 is very good and cheap

Desolder braid with flux

Heat Gun

Dim bulb tester

Fuses - slow blow and fast blow, 250V 2A-10A

Jeweler's magnifying glasses with light

Calipers

Toothbrushes

Something to discharge capacitors - I use a 100W bulb in socket with exposed wires - can also use a resistor (don't use screwdriver method)

De-Oxit D5

CRC QD Electrical Contact Cleaner

Isopropyl 91%

Acetone

Thermal paste

Kapton tape

Windex

Wire/Cable - all kinds

shrink tube - assorted sizes

Other Tools:

Variac

Scope

Function Generator here is a good, cheap kit

ESR Meter for testing capacitors good, cheap one

LCR Meter for Caps and Inductors

Desolder station - hakko also has a good one

That's all I can think of for now. Have fun and don't electrocute yourself.