hi icod
Yes, go for it!
I did Russian at Cambridge, have lived in Kazakhstan for 3 years and still can't speak very well, basically still constantly flummoxed by the grammar. The grammar is a total sod. The only way is to literally learn all the tables, and then just learn one sentence you can remember for each ending, however silly.
Like 'with the red umbrella' to practise the instrumental: 's krasnim zontikom' or whatever..
BUT it is v rewarding. Russians are great.
the worst thing is the verbs of motion. check out the little films from this link under 'verbs of motion' section, which cleared it up for me once and for all..
www.departments.bucknell.edu/russian/language/
as for the numbers declining, this is enough to get you very depressed, so just avoid using numbers and above all never try to say what happened in a particular year.
it's a warm, wacky and tragic culture, you get into it and can't get out again!
this didn't make sense, sorry..
best of luck!