i am lucky as when i did my abf engine conversion, i fully degreased the block inside and out. oil pump new vw, head rebuilt and acid dipped. it was immaculate. still is.
but i still do 2 oil changes. oil and filter from vw/tps is £10 for me with cti discount. thats a vw filter and synta silver, a litre spare as i buy 2 of both.
i do one change to clean it out, then a week later change it again. its always golden. smells lovely buring off for the first few drives.
i would definitely drop your sump, clean it out and the pump pick up. change your oil with the cheapest crap you can find. go for a good drive. come back and fill up with proper oil. synta from vw. dont mess about and use anything else.
may as well do your coolant while your there. g12++ please