Using the components included...
Using the components included in the kit, reassemble the all of the pieces in reverse order of disassembly. The World Class T5 rebuild kit from Summit Racing comes complete with everything needed for a simple freshen-up.
What You Need
Provided you didn't grenade the gears, a simple rebuild kit is atop the list of must-haves. Summit Racing sent us a Ford Racing World Class T5 rebuild kit (PN M-7000-A), which includes bearings and races, blocking rings (sometimes called synchronizers), shims, clips and snap rings, a front bearing retainer, a tube of silicone sealant, and three quarts of ATF. With the exception of tools and instructions, the 94-piece kit has everything you need, and it retails for $249.95 through Summit Racing. If you do have a busted-up T5, some good sources for parts are Astro Performance Warehouse, G-Force Racing Transmissions, and Hanlon Motorsports.
Basic handtools are necessary, like flathead screwdrivers, metric sockets and a ratchet, punches, snap-ring pliers, and a hammer. However, some other less common tools are needed as well. A T40 Torx bit, parts washer, gear puller, dial indicator, press, press plate, and torque wrench are probably not in everyone's garage.
Teardown
As you take your transmission apart, it's important to inspect every piece for abnormal wear and bent or broken parts. If any other parts are damaged, replace them as well. This is very crucial for the longevity of your transmission. A magnifying glass is nice to have so you can closely inspect parts for cracks.
Also, the job will be much easier if you lay every piece out on a bench in the same order you remove it. This will prevent mixing up parts. Some components look very similar to others, but are slightly different. It's very important that you keep your work area as clean as possible, as dirt can cause premature wear on your new components.
Reconstruct
Since the tapered bearings are pressed onto the gear shafts, it is necessary to use a press to remove the old and install the new ones. It is essential that the bearings are pressed on straight and that they do not get damaged during installation. One small nick in a roller could destroy a race very quickly.
Soak the new blocking rings in ATF overnight. This will lubricate them for assembly and prevent premature wear upon initial use. Think of it like priming an oil pump before you start an engine for the first time.
Once all of the components have been cleaned and inspected, assembly can begin. Simply install the parts, piece by piece, in reverse order of disassembly. Once all of the parts are back in the case, but before installing the tailshaft housing or cover, move all of the sleeves one at a time to check for clearance and proper operation. Make sure each gear, including Neutral and Reverse, work properly without binding or grinding.
Now, follow along as we show you the basics of a T5 rebuild. Since we can't show you every step, we hit all of the main points to give you an idea of the process and the level of difficulty.

Use press and press plate...

Use press and press plate to remove and replace the input shaft bearing.

Remove First gear and blocking...

Remove First gear and blocking ring, and then remove the Second gear snap ring.

Remove the Second gear retaining...

Remove the Second gear retaining ring with a couple of picks or small screwdrivers. The main shaft can be removed at this time.

The countershaft bearing must...

The countershaft bearing must be removed in order to remove the countershaft from the case. Be very careful as not to damage the case while removing the bearing.

The main shaft can now be...

The main shaft can now be removed from the top, cleaned, and fitted with new synchronizer blocking rings.

The countershaft is the solid...

The countershaft is the solid machined shaft at the bottom of the case, and is held in by a bearing retainer. Remove the retainer with a T40 bit.

Small metal particles will...

Small metal particles will be stuck to the magnet in the bottom of the case...

...along with other components...

...along with other components you may have dropped during disassembly. Clean the case and other components thoroughly in a parts washer.

Because it is recessed, the...

Because it is recessed, the bearing on the front of the countershaft must either be removed with a special tool or with a cutoff wheel. We chose the cutoff wheel. The new bearing can be installed with the press.

Install the countershaft into...

Install the countershaft into the case and press in the new rear countershaft bearing.

Once the transmission is reassembled,...

Once the transmission is reassembled, it is necessary to check for endplay. Using a dial indicator, use the shims provided with the kit to achieve 0.000-inch overall endplay.