It really depends on the condition of the original black and white. If you upload a the two images or maybe what you have so far it might help in identifying what steps might be needed to make your new image blend with your old image. Without seeing the image, I can only guess...

Maybe...

Use levels using the output sliders to reduce contrast.

Use Brightness contrast filter to reduce contrast and/or brightness.

Use Hue/Saturation layer to create a black and white which better matches the tone of the original. In the Hue/Saturation dialog, reduce the individual color saturation level to 0% saturation instead of using the master. (Change setting from the default master to the individual colors in the drop down box in upper right hand side of Hue/Saturation dialog.) After each color is set to 0% saturation, adjust the individual color lightness and possibly hue to roll your own black and white photo effect.

Try using the grain filter.

The link below shows one method of aging a photo. If you skip to page 5 and 6 it shows using the grain filter and adjusting the levels output sliders. Keep in mind since adjustment layers have a mask you can use a brush with black paint to make the effect such as a levels fade in and out. (Tip: Try a brush made for clouds on the levels adjustment layer mask to make the contrast patchy.) Keep in mind you can do this in more than one adjustment layer...i.e. you could set the overall contrast with one levels layer then add a second levels layer over this one and use it to make the new contrast patchy.

Here's that link:

http://www.photoshopessentials.com/photo-effects/old-photo/page-5.php

Page 5 shows the grain filter being applied. Page 6 shows the levels output being used to reduce overall contrast.

If you need scratches and/or bends, the answer is the paint brush and white paint or use a scratch overlay. Look around the net for scratch brushes or scratch overlays.

Use a seach term like scratched Photoshop brushes.

You can also try using the dust and scratches filter to get a faded glowy look that exists in some older images. See the tutorial linked below to see what I mean.

http://www.idigitalemotion.com/tutorials/guest/old_looking_images/oldl ookingimages.html

The above uses a layer mask. If you don't have PSE 9 or PSE 10, you can either use a clipping mask (clipping group if it's older than PSE 8) to make the dust and scratches effect patchy. You can alternately use a soft tipped eraser on the dust and scratch filtered layer and erase where you don't want the effect. I would recommend either using a mask or if you must use an eraser to use a soft edged eraser tip and to set the opacity at a low setting so you can slowly strip away the effect. (You could also try using a cloud brush with your eraser tool to make it erase patchy. Just be sure to switch that brush out before you finish this project or you'll be wondering why your eraser is acting funny at some later date. )