Repair / TÜV costs – Omega 2.2 16V

Hello Omi fans, now it will be time to get TÜV again on my Omi and replace various “small parts”. Before I go this step, I wanted to ask if I can also use spare parts from the bay and which manufacturers deliver good products from there. The parts are installed in a free workshop of confidence. Achso, and which parts costs on average are to be expected, as well as how many work units to which work step are needed? Because there are still immense differences. For small general overhaul are on my list: – starter – petrol pump – battery – 2 x shock absorber rear – possible crackers ( already for 2 years in the final stage ) – complete liquid change (oil, cooling water, brake fluid) – new seat heating driver side – front panel (stone impact) – possibly new climate compressor (climate does not start) – brake lines on both sides back Many thanks in advance for your assistance.