The Crosman 1088 Pellet/BB is rated at 400-430 FPS
See the related link at the bottom of this page to see the Crosman 1088 parts manual.
see the link below for the owners manual
It would really help if you stated the manufacture of the 1088. So I'm going to guess it's a Crosman. See the link below
Yes but it is best to make it a head shot, or the squirrel will suffer and die.
Crosman has a web page for their owners manuals and part list. See the attached web page. you will find your 1088 listed about half way down on the page. The parts last will give you an exploded view of the gun. See the related link
Best to take it to a authorized repair center
See the link below. This is for the 2100 not the 2100B or 2100W.
see the link below for the Owners manual.
Crosman offers a parts diagram for most all their guns and rifles. see the link below for your recruit. Parts are still available for this rifle through Crosman's home page.
It's hard to help you, considering you did not say what is wrong with your airgun. So here is what I suggest. Crosman offers a service to locate shops that repair older Cromann products. See the link below.
If it's not on the outside then very possibly it's under the grip cover