I need a manual for a Jason Discoverer 454, model 313

Look on Ebay, or contact the manufacturer

Maybe and maybe not. Most of these are very low cost telescopes. If something major is wrong then NO.

If all you need are a few accessories look around this web site and check the prices.

http://www.agenaastro.com/

Read my tips on my profile page.

No one makes manuals for these small telescopes. However MEADE BRAND scopes have a web site with all of their manuals. Look under the REFRACTOR heading for one that is similar to your scope.

http://www.meade.com/manuals/index.html

Sorry no manuals available for that small telescope.

All of the manuals for Bushnell are located on this web site. Find your telescope model, and download a free manual.

Look down the page:
http://www.opticsplanet.net/bushnell-warranty.html

Put the eyepiece with the largest number written on it into the telescope. DO NOT use the 2x barlow if you have one. Go outside during the day time and practice focusing on a distant object.

The moon should be your first target.

Bausch & Lomb Sporting Optics were purchased by Bushnell in the 70's. Bushnell continued with the Discoverer line. Try searching Bushnell online for the product manual. They still have many PDF's of older models that carried the B&L brand on them. Thos branded Bushnell are identical to the B&L model of the same specifications and configuration.

Here: Find your telescope manual-
http://www.opticsplanet.net/bushnell-warranty.html

These web sites should help you--

http://www.opticsplanet.net/baush-lomb-telescopes.html

Read all the links--

This is a 60mm refractor not much larger than a 50mm pair of binoculars. You will not find a replacement lens, unless you can remove one from another telescope of the same type.

Sorry