KayCee,
We all feel for you!
This forum has encouraged me to tackle some jobs myself and it has given me real satisfaction (and saved money). Perhaps you can be encouraged?
I replaced my front discs and pads yesterday. It took me less than three hours and I have to sit on the pavement (fortunately very few pedestrians). The pads and discs cost £94 (AGR Automotive) and some ProSlip pin, pad and clip greases cost <£10 with LOC discount. Just changing pads is much less work and time.
The seized rear caliper can almost certainly be freed off, greased with proper grease and put back. (I've done this too.) Lexus don't do this, preferring to change the complete unit. (The cynic in me wonders if they send your old caliper to be refurbished and resold.) There is a little video tutorial on this site. There is probably a video for the front discs and pads but I haven't searched.
Can't help with the fuel pump insulator sorry.
Have a go!
John