Cost to replace main seal

I checked fluid level and seems ok, a little fluid has also backed up through the tube. Van seems to run fine.

I have already replaced tps at throttle body tps module keep getting codes and low engine power light on dash . Seems to happen after clearing all stored codes then driving aproxamatly 20 miles or 30 to 45 minutes local dealer says after I changed tps I needed to also change plug also so I did that and same problem next was module and same thing now Chevy dealer says i needed to cut back engine harness back to lenght of wires that came with replacement plug and that will cure problem . So far everything they have said was wrong with it and needs to replace has done nothing to solve reoccuring problem. I dont think that cutting back harness wires to length of new plug and wires will do any thing.As far as I know they are just guessing as to the problem. have been employeed as mechanic for many years and never run into this problem. Tired of just throwing parts at this thing
thanks and sorry for long post

earlier models

The pump just quit. I was also having trouble with dash lights coming on and radio not shutting of when opening the door.

it's connectedd at some point my a/c blower does'nt blow air in front but always in dashboard

My 2005 Chevy express 3500, I changed the heater core because it was leaking, now I have no heat. Did I do something wrong?

i put new termostat and redeter but the gadge shoes over heating what is the problem.

Where is the fuel filter located?

i have replace the ac contol unit on the the center of the dash but still doing the same thing

i have replace the ac control unit but
still doing the same thing any suggestion?