91 Jeep won't start - but battery should be good. It turns like normal but won't "catch". 91 Jeep Cherokee

Hi, My 91 Jeep Cherokee only has 70k miles on it. I only put 500 miles on it a year at most but have the oil changed and use premium gas in it. It's been super faithful. For the last two months I've noticed that it was taking longer to start up than usual, though it doesn't make that dying... show more Hi,
My 91 Jeep Cherokee only has 70k miles on it. I only put 500 miles on it a year at most but have the oil changed and use premium gas in it. It's been super faithful.

For the last two months I've noticed that it was taking longer to start up than usual, though it doesn't make that dying battery sound you get when it's your battery. Finally, last night, it wouldn't start at all. A jump start got me going.

Details: It's had the usual repairs over the years, exhaust systems, brakes, pads, belts, new radiator, spark plugs. It gets yearly check ups but it doesn't get much use. I checked all of the connectors under the hood that I could find. I read here that it wouldn't be the alternator because the alternator isn't used until the car actually starts (catches, gets going, does more than make the normal pre-start noises). I'd also like an idea of what I might be charged to repair. there are several shady auto shops here and I have "idiot" stamped on my forehead.
Thanks much.
Update: Thank you all for your suggestions. UR all super fast. The shop where I dropped it off just called and here's the deal. Pls let me know if the price looks right , okay ? 3 fuel relays (need replacing) 1 "Cam" sensor Tune up The cost is $665.00 If I skip the tune up it's :... show more Thank you all for your suggestions. UR all super fast.

The shop where I dropped it off just called and here's the deal. Pls let me know if the price looks right , okay ?

3 fuel relays (need replacing)
1 "Cam" sensor
Tune up

The cost is $665.00
If I skip the tune up it's : 328.00

Since I can't afford $665.00, I said they could start the work but skip the tune up. I remember seeing coupons for much less (tune up) in the mail . Unless those are tricky coupons... I asked which work was absolutely manditory because I can't afford $665 and they said the Jeep would start up okay 'for a little while' if I okay the relays and cam sensor replacement.

They did $700 of repair work just to pass inspection in December (which I authorized). Back then , the shops would give me different diagnosis' and I didn't know who to believe. So I went with the lower $500 one . Jiffy Lube tells me they give me a tune up every year (not just topping off the fluids).
How much should a tune up cost ?
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